Thanks again for all your advice.
I bought a used Yamaha RX-V995 5.1 receiver and I'm using it with the ELAC floor and center speakers and the SVS sub. It's nice to have the center speaker for TV, but the surrounds aren't worth draping wire across my living room and they sputter when the settings aren't right, so I disconnected them, at least for now.
I hooked up the Optimus speakers on the B channel for comparison and tried both of them with the two impedance settings. The best sound is with the ELACs on the 8-ohm setting. I'll just have to be careful. I may add a computer fan with a thermostat, although it already has a fan built in. The Yamaha has a protection circuit, which my old receiver didn't have.
The ELACs with the Yamaha sound great and really fill the room (almost too much gusto). The improvement in audio quality over the Optimus speakers is really only noticeable if I'm listening to a well-mastered CD, which would sound great on the cheaper setup anyway. So, as much as I really love the new setup, my world was not cracked wide open by the sound. The receiver remote is huge and hilarious, as are the effects options (Disco, 70-mm Sci-Fi, etc.), but the interface is very simple and intuitive and I won't loose the remote between the couch cushions, so that's good.
What really needs the most work is the phono quality. The phono pre-amp in the receiver is better than the one in my turntable, but I think I still want to upgrade my turntable and maybe the pre-amp. I'm also curious to borrow a Cambridge axr100 demo from our local shop (ListenUp) for comparison. I'll update if I do.