Eh, I'm not sure. PHBII has some brokenness in at least two of its classes (Duskblade and Knight can be pretty broken), and Spell Compendium has some broken spells in it.
It seems like you've already got the books I'd most recommend anyway.
I suppose I'd suggest Complete Adventurer and Complete Scoundrel. They have good material in them and, at least as far as I've seen/heard, have better balance and general usefulness than some of the other so-called "Complete" books.
The Expanded Psionics Handbook generally requires you to do a bit of houseruling, or get the errata (such as by purchasing Complete Psionic, which has some or all of the errata; I think it has all the XPH errata?), and even then you may need a bit of houseruling. Also, psionics isn't for everyone, so I dunno if you're particularly opposed to psi or ambivalent or well-inclined towards it. I like psionics, but I also recognize that the current edition doesn't quite fix it as well as it should've. Some of the powers need to be adjusted with errata from Complete Psionic or something, to be even remotely fair, and a few are still too potent then. The Soulknife is a weaker base class in the XPH than it was a prestige class in the 3.0 Psionics Handbook (where it was quite alright and useful for what it did). The Complete Psionic prestige classes and feats and such for Soulknives makes them somewhat better, but still doesn't make up for their bit of deficiency (or their wierd identity crisis in 3.5).
Also, I don't like 3.5's replacement of power point costs and requirements (for feats; powers still work through points as in 3.0) with psionic focus; it's a lame mechanic that sucks and is only decent for a few psionic feats. Similarly, I don't like 3.5's exaggeration of crystal themes and lame naming conventions. The previous versions of psionics had better names in most cases and less emphasis on crystals, whereas 3.5 overdoes it. 3.5 both improved psionics and gimped it at the same time (it's still quite useable and effective, generally, but so many things have been eliminated or changed or ruined in 3.5's psionics revision). It's a mix of good and bad, and overall I just don't like how it works in 3.5.
The 3.0 psionics worked kinda more like magic yet still retained some of its old flavor and uniqueness, despite a bit of drift; 3.5 totally abandoned most of the stylistic limitations of psionics and the advantages of it, in favor of making it a sort of wierd variant on magic that nonetheless suffers some strange limitations and drawbacks despite the apparant reckless abandon in removing most of the old psionic style and limitations; if that makes any sense (because it doesn't; they both removed limitations and threw in new ones, making it copy most things magic could do, while simultaneously limiting some of its functions that were previously fine or useful).
