Wired PC getting half the downstream speed as wireless laptop

Just wanted to update this thread to say that the limitation was indeed the switch built into the Trendnet TEW-633R router. I bought an amped wireless R10000G, since they offer a 30-day money back guarantee when buying directly from them. No problems getting 50 Mbps down, 10 Mbps up on PCs wired through an HP ProCurve switch, which in turn is wired to the router.

I've no idea if other Trendnet routers might have this problem, but using smallnetbuilder.com one can see the internals:

Internal Details
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Internally, the TEW-633GR contains the same main components as the DIR-655—namely a Vitesse VSC7385 switch, a Ubicom 5160 processor, and an Atheros 5416 baseband/MAC chip and AR2133 3x3 MIMO 2.4 GHz radio (AR5008 series).

Ubicom and Vitesse were new to me, but since I had no problem achieving full speed wirelessly, all signs point to the Vitesse switch.

Hope this all proves useful to someone in some way.

Cheers.