Well I found out that the modified version of poclbm has been discontinued as a high-efficiency miner for bitcoinpool. So that answers that question. They recommend using Phoenix now (which I have already switched to).

But my earlier question about solo mining still remains. If I connect multiple miners to my "bitcoin.exe -server", does it effectively sum up all the hash-rates of the mining computers? Obviously this is how a pool works, but these pools have complex job-assigning and tracking software above and beyond the simple "bitcoin.exe -server".