The DWA-140 works great with the DIR-655. It's USB, so as long as you've got USB 2.0 (450 Mbps) you should be good for N connection speeds of up to 300Mbps. I usually get a 200+ connection through 2 walls (40 feet I'd guess). Actual speed is about the same as 100Mbps Ethernet, as long as there's no G activity (my DIR-655 is set to mixed-mode G/N.
You should be getting about the same results with the DWA-142, if the G device is offline. Onless you're having problems I would stick with the DWA-142.
BTW, bought the DWA-140 online at J&R - was cheaper than Newegg (and still is).