I've been looking at the options recently and for the money the Netgear EVA-8000 seems like the best choice. Recent sales on eBay range from £72 to £120.
This link below is a little out dated as recent firmware updates have added support for .mkv, iso, ifo and other files
http://www.netgear.com/Products/Ente...s/EVA8000.aspx
The Popcorn Hour A-100 looks to be the top product but the price to prohibitive, the 360 doesn't have enough functionality, the PS3 is good when used with PS3 Media Server but again the price is prohibitive if you only want an extender and it doesnt integrate with VMC.