If you're looking at dedicated DVR boxes, I've no experience with those. Sorry.
I do have some experince with PCs that are built with this in mind. Brief rundown, I have a 1.8GHz P4, 1GB Ram system running an ATI All-In-Wonder 9600XT. It came with ATI's Remote Wonder II (which has since died and been replaced under warranty that expired last month). The card itself works great for sending video out to my ancient (circa 1987) TV, and records just fine. The included software is frankly a POS and a pain to get stable. ATIs support as been lackluster as well. I've been testing SnapStream's Beyond TV 3, which so far as been stable out of the box (day 5 of a 21 day free trial). It records, is not difficult to program or update the schedule listing, and has a plugin for the Remote I use.
Cost of the box was about $400 for parts (case, MB, CPU and RAM), since I had spare drives hanging around for recording, CD and DVD playing.