Let me see if I've got this right--the hardware levels a2, a3, a4 represent physical changes in board pieces/parts and there is firmware that correspondsto these hardware levels?
I'm simply in the market for a new router and have found no one is particularly happy with their routers according to Amazon metrics. D-Link customers seem to be best compared to Belkin N+ (30% unhappy) and Cisco WRT310N (40% unhappy), but the D-link firmware discussions will be sufficient to stop me from buying until the noise stops.
Customer   D-Link DIR-655      
Rating   Reviews   %   %+
1   440   56.6%   56.6%
2   143   18.4%   75.0%
3   57   7.3%   82.4%
4   38   4.9%   87.3%
5   99   12.7%   100.0%
Total   777   100.0%