If wireless range is what you care about, then I agree the WHR-HP-G54 is the better buy. The G54 is also the better choice if you have multiple PCs across multiple floors because you can setup two -- for much better wireless coverage -- in a bridge configuration very easily. Bridge options are very limited on the 4300.
However, if your priority is wired and p2p performance, the DGL-4300 offers superior price/performance at $70 relative to the Buffalo at $59. The throughput on the DGL-4300 is superior to the WHR-HP-G54 with DD-WRT. The QoS on the G54 with that 3rd party firmware is also inferior to the QoS you get on the 4300.
As far as Pre-N being obsolete by year's end, that may or may not be the case. The DIR-655 uses the Atheros AV11C1 (rev A3) part -- part of the Xspan series -- which Atheros expects to support the final 802.11n standard. The current DIR-655 firmware already supports Draft 2.0.
http://www.atheros-xspan.com/index.php?page=Experience&sub=XspaN+FAQ
Even if you don't care about 802.11n, the DIR-655 will still function as a 802.11g MIMO router. D-Link lets you choose the wireless mode you want in firmware setup.
The DIR-655 uses the
Vitesse VSC7385 gigabit switch found in a number of newer 4-port gigabit routers from Linksys, Netgear, and others. The chip supports jumbo frames, but the current D-Link firmware does not. It's unknown whether the D-Link firmware will ever support jumbo frames.