I can only give you my opinion on the Yamaha RXV-2700
I got it on 12/07 and I'm happy with the receiver ... 140WPC, HDMI, opt, etc. before the Yamaha I used a Sony STR-DE897 but the Yamaha is much better
The big difference between the 1800 and 2700 is the True HD ... you can compare both model here
www.yamaha.com/yec ... I'm not sure how you plan to hook up your system (TV, Sat/Cable, VCR, DVD, etc.) this will make the difference to choose your receiver; if you're planning to get a Blue Ray player and connect all video signals through the receiver your best bet is the 1800 ... but if you will connect the video signals to TV and the audio to receiver (like me) you'll be fine with the 2700 ...
Good luck with your purchase
