Polk RTi 8/10 vs Monitor 70

[BLindsay]

So i should be able to get my setup by christmas but originally i was gonna do

Monitor 60's
CS2 center
Mintor 40's


newegg had the monitor 60's in cherry for like $140 each but they cant seem to keep stock on them so im thinking i might have to get the monitor 70's (not that thats a bad thing) but the monitor 70's are like $200 each and the RTi 8's are $200 each and the RTi 10s are $280 each. whats the difference between the Monitor 70's are the RTi8's and is it worth $80 each to get the RTi10's (hell the 12's are $350 each)

Also id imagine if i got the RTi fronts i could use the CS2 center or Monitor 40's in the rear? which in that case would driver the overall cost of my system up alot because the RTi rears and center are alot more