Nah, that's not really an option. The races and classes are only available in the AU book and the AE book (though a scant few have been previewed on Malhavoc's website to some degree, and one or two are found in other books, such as the Totem Speaker base class in Transcendance; it's sort of a druidic mediator class, that sprang up after the return of the dragons, trying to maintain balance and peace between the dragons and giants, nature and civilization; they are sort of a cross between Totem Warriors and Greenbonds).
Transcendance, as mentioned by others, details various new options and variants for improving characters in different ways. For one thing, it introduces the Totem Speaker class, which has a medium BAB, high Will saves, mediocre HD, above-average skills, medium spellcasting progression (like a Runethane, Witch, etc.), several totem trait choices over time, and few mediation, spirit-talking, and vitality benefits from the Green over time. Transcendance also includes replacement levels, more or less like substitution levels in D&D but not so race-related. It adds a few more feats other other abilities for each class to help them specialize or differentiate themselves, and includes other new options for the classes, like Akashic items, Exotic Combat Rites, and feats that require a level in the appropriate class and involve that class' features in some way. There's a prestige class or two mixed in there, such as the Living Oath prestige class for Oathsworn.
Transcendance also adds the ability-evolution classes, a set of six pseudo-prestige-classes that work similar to the Evolved racial levels detailed in Arcana Evolved. Each of these classes goes up to level 5 and improves the associated ability score by 2 points of the course of those levels, along with granting some additional benefits appropriate to their theme (for instance, the Strength Evolution levels can increase a character's size slightly with some limitations, while the Wisdom Evolution levels can increase a character's effective spellcasting every other level). The book/PDF (I bought it in PDF from RPGNow) also introduces some Runic Affinity feats for any character to take (though each may only take one), some Tylonian crystal weapons/armors/etc., and some Arcane Evolution options, granted by some replacement levels, which provide benefits based on a chosen spell descriptor such as air, electricity, force, etc.
I haven't read any of my Arcana Evolved PDFs fully yet, only skimming parts of them so far, since I only bought them a few months ago, so I don't have any direct experience or opinions on how it works in play yet. I bought Arcana Unearthed years ago in the bookstore (the FLGS didn't have it), and am more familiar with it, but haven't had a chance to play it run it yet.
AE's only new base classes are the Totem Speaker (in Transcendance) and the Ritual Warrior (in Arcana Evolved), as far as I know. I don't have an opinion yet on the Ritual Warrior, but other posters have already described it a bit. My first impression is that it might be a bit weaker than other AU/AE warrior-types, but I'm not sure, it might be on-par or a bit stronger. *shrug* Arcana Evolved adds the Dracha race (a winged race of dragon-created warriors, able to glide somewhat, more physically adept than the mojh). AE adds a few things for various classes, but not a lot. The Champion of Justice and Champion of Knowledge choices for Champions were added. Not much else as far as I've noticed (though I haven't finished reading the PDF yet).
Roleplaying-wise, Arcana Evolved has some expanded descriptions for the races and other stuff, and of course adds a bit of setting information related to the return of the dragons. It has only a few pages regarding lands outside Dor-Erthenos itself (two or three pages on the lands immediately around Dor-Erthenos such as Zalavat and Thartholan, a page about Pallambor, the land just west of there, under a page of detail on Skaraven to the south, and that's it).
Legacy of the Dragons, the monster-book, seems pretty good, but again, I haven't had a chance to see it in play yet. It includes notes for use of the critters in 3.0 and 3.5 D&D rules (such as 3.0 and 3.5 D&D versions of Damage Reduction). There's a Conversion Appendix in it for using the creatures in non-AU/non-AE games, such as replacing particular feats or gear of the creatures with equivalent ones from the D&D core rules/SRD. My impression from reading some of the creature entries is that, with the conversion appendix, you don't need AU or AE (and I don't think you need either particular version of those rules, it seems useable with both versions).
I'd recommend all three books, but if you already have The Diamond Throne, then you can do just fine with Arcana Unearthed instead of Arcana Evolved. I bought AE mostly because it was on sale and I didn't have The Diamond Throne yet, so I figured it was worthwhile just to get The Diamond Throne material along with the added or revised material that wasn't in my copy of Arcana Unearthed. AU will provide you with most of the AE book's material that you don't already have, though, since you already own The Diamond Throne. AE only adds a few things, like Evolved racial levels, Evolved class levels (21st through 25th), the Dracha race, the Ritual Warrior class, and little more. You could use Legacy of the Dragons or Transcendance without AE, though I think Transcendance's ability evolution and arcane evolution stuff might not be useable without AE (I forget if Transcendance details the evolution-level costs and such, since they are detailed in the AE book).