There are some, Cocktail Audio's X10, which, for the 2TB disc drive comes in at around £450, or less for the 1TB version. No doubt others are out there, but there's not too many around your budget I think.
I think most things tend to be heading in the way of NAS drives and something like a squeezebox touch. Depending on what kind of capacity you're after the two could be had for around £270 (Based on a 500GB one). There is also quite a few people on here who will vouch for it in terms of sound quality. Just a thought . .