I am looking for a mid-range router that is capable of supporting dd-wrt. Does anyone have any suggestions?

The ASUS RT-N66U is a Dual Band N-Router (2.4GHz and 5GHz bands) with lots of RAM (256Mb) and FlashRAM (32Mb), so it is well equipped to run DD-WRT.
I run mine on VF 50/2Mbps cable with a (VF-supplied) Cisco DPC3008 modem.
Nice hardware, good user interface, excellent wireless performance.

I've had one for a few years. Never given me any trouble and consistent fast speeds. This is now good value (was a bit pricey when I got it, but you pay for quality). Still looks quite nifty too.