To partially answer my own question, the latest version of aqua4itunes (3.5.0) works with iTunes 7.6.1:
Although the aqua4itunes website indicates that this version is "For iTunes 7.5.x", it seems to work fine.
PS: Ah, notice the flat controls like you might find on a real player rather than primer grey oval blobs that you might find on a fisher price toy player.
Its a minor complaint but for the record, the one element I don't like in Aqua4iTunes is the Aqua-tized volume button (see screenshot). I don't recall that button ever being Aqua in iTunes 6 or below. I think the author of Aguat got it right by leaving that one button alone. It looks like a little pearl, which stands out too much and is a tad cheesy IMO.