Summit vs. Theo & Pricing

[Stereonerd]

I recently posted about the Theos I bought to replace my Puritys, and the poor bass I was getting from the Theos. I subsequently replaced with a better amp (a second-hand Bel Canto... I'm on a tight budget) and I have to report that my problem wasn't the Theos, it was my amp. The bass output of the Theos is prodigious! In fact, I'm astounded at the difference between the Puritys and the Theos: a much wider soundstage, incredible boost of clarity and dynamics and I'm finding that they're an absolute pleasure to listen to. But now, a second hand pair of Summits has come onto the market and I'm wondering: WOULD THE SUMMIT MAKE THE THEOS SOUND LIKE RANK AMATEURS? Two other questions for the experts out there: How much would you expect to pay for a pair of Summits purchased new 8 years ago but never used? These ones are going for approx US$7000. Were there different iterations of the Summit prior to the advent of the Summit X given that the Summit first came out in 2005? And what size room does a Summit need to sound great in? My listening room is approx 20 feet long and 17 feet wide.