What would you recommend for a preamp?
In your current room you don't need to add pre-amp and/or amp.
Onkyo TX-SR608 is a very solid AVR and have more than enough power to drive these speaker to very loud levels.
If you decide to use speaker in MUCH MUCH bigger space, you could just change AVR with pre-outs and add amp
Going dedicated pre-pro is a costly proposition, and using AVR for pre-pro is typically much cheaper, while not sacrificing much (if any) of SQ...
If I would need to pick AVR for pre-pro duty - I think Yammi RX-A700 would be good choice (or A800 if you need video scaling features) add Emotiva XPA-3 and you could squeeze out every bit of potential out of RC-30 and if later on added Energy RC-LCR center speaker.