I just got a lenovo g570 on amazon for $434. had to shop around too find the best deal. nice 15.6" screen, windows 7, 2.5 ghz i5 processor, 4gb ram 640gb drive. ordered on a sunday and it showed up on tuesday. no problems, but i don't do pc based audio tracking. I just use this machine for internet stuff, axeedit, band in a box, and the occasional copying of hd shows for replay later. also, i'd use your current machine until it craps out, unless it's too slow.
At work we have about 200 computers, I'd guess. For laptops we've used toshiba, dell, sony vaio, now HP. They've all been good quality, but I think I'd prefer the sony least (I like the lenovo better than most).
$800 is way more than you need!