Just make sure the 320 or 520 has enough power to handle LMCE. I have worked some with the dsm-510 and returned it because it way underpowered. The GUI that comes with it is slow as hell to the point I looked no further. LMCE is not the lightest application out there.... The Appletv is the direction I have been looking at because I think it has alot more power at about the same price point (not positive on the specs of those 2 boxes).
Ebay you can get a an appletv for low 200s, dlink 320 is $99 at Frys in Cal. and the 520 is $169 the last time I looked.