Just realized that I didn't address your question directly. I probabl should have tested actual throughput with the DLink router talking t the DLink pc card vs. the Belkin pre-n router talking to the DLink p card - but I didn't.
A couple of issues involved here:
If you're actually getting better-than-G throughput due to proprietary mechanism such as Atheros "super g" or Broadco "afterburner", then it's quite possible that throughput between a ne Belkin pre-n router and your legacy "g" card will be slower than it wa with the proprietary technology.
If, however, you're using "standard G", at 54 mbps signaling rate, the I believe you'll actually see better results with the new Belkin route than you would with your old standard G router talking to your legacy card -- although I can't swear to it. It would have been interesting t try that out.
When I first installed the Belkin pre-N router, I left my old D-Lin "super g" cards in my wireless pc's. Everything connected up ver quickly, and it felt - subjectively - that the connection wa significantly quicker than it had been with the DLink di-624 running a a claimed 108 mbps signalling rate. But it was when I installed th Belkin "pre-N" card in the pc that I saw the really dramati improvement in speed that's promised by the Airgo mimo "pre-N technology in the Belkin router.
I know this probably won't talk to the 802.11n standard that will b finalized in the next 18 to 24 months. But as far as I'm concerned, a the minimum, it's a souped-up proprietary "super G", no different i the compatibility issue than Broadcom's afterburner or Atheros super g None of the proprietary speed-boosting G technologies will "talk" t the eventual "n" standard at anything other than standard "g" rates Belkin's version is somewhat pricier than the others -- but it's muc faster and has better range -- and the difference in performance i worth the difference in price for me, and the compatibility issues ar NO different than you'd see with ANY proprietary enhanced "g technology.
Last note - more directly in answer to your question about improvemen with legacy network adapters:
The Belkin wireless connection to my old Dlink dwl-g520 wireless car proved to be more stable than the Dlink di-624 connection to the sam card