I think you might enjoy Ptolus, which is just about to come out from Monte Cook.
1. Magic / Power level - Set to default at medium.
Now before people jump down my throat over the level of magic, I think a lot of people took a minor comment about "wizards being everywhere" in the city of Ptolus out of context. It's not a high-magic game. All that was meant by that comment is that people are familiar with magic...they know it's around, it has a presence in the city, it has had an effect on society. It also specially says magic isn't common among the commoners, just that they are aware of it (and have some laws to curtail some use within city limits).
Ptolus is a medium magic setting, and medium power setting. It's Monte Cooks D&D playtest setting in fact, so the level of magic is set to essentially the default balance setting for the amount of magic and power the authors predicted your average game would contain. And, it is 100% v3.5, with none of the quirky 3.0/3.5 transition issues some setting have (which, of course, is because it's just now coming out).
2. Modules / Series of Adventures - Yes and Yes.
Ptolus has modules that come with it. Apparently, there will be enough material included with the setting (including the CD that comes with it) to cover your players from 1st to 20th level without ever really needing to buy anything else, all with a linked series of adventures that are supposed to be about 50% city based and 50% dungeon based.
3. Psionics Built In - Unknown but probably yes.
As for Psionics, I honestly do not have the answer to that question with the Ptolus setting. I believe that the author of most of the Psionics stuff is one of the players in the still-ongoing Ptolus game, so I think it is likely there is built-in psionics, but I really don't know as the book is just about to come out but it isn't quite here yet.
4. Rules Changes and Overabundance of Sourcebooks - No and No
As for "doesn't change the rules to much or require many source books to be purchased", Ptolus definitely meets that criteria. No rules changes really (as, again, it was the playtest campaign for D&D in general), and only the one book for the DM to buy. For players, they get the Player's guide for free in PDF format or for literally a couple of bucks or less in hardcopy format.
Overall I think it might be your style.
You might want to check out their free players guide to Ptolus, over at DriveThruRPG.com :
http://rpg.drivethrustuff.com/catalog/index.php?cPath=49_554