replacing rears and amp, help with settings?

[CorNut]

I have a car that came with a factory amp and sub. I recently purchased an "Infinity Kappa-Five" 5 channel amp. It does 75wx4 @ 2 ohm and 300w sub channel at 2 ohm. The fronts I have installed are some 6.5" Infinity Reference 6030CS 2ohm components that are 90w RMS. My current rears are some 4 ohm Clarions that are really old and they don't sound very good. I found some 2 ohm Infinity Kappa 629i coax's that are 75W RMS & have a built in crossover for the tweeter. I also found some 2 ohm rears that will match my fronts, they are Infinity Reference 6032cf's but they're only 60w RMS. I don't see a built in crossover for the tweeter like I do on the Kappas. They are pretty similar in price, should I match the rears to the front or should I go with the Kappas since their RMS handling matches my amps RMS wattage?

My amp has built in crossovers, the front channels, rear channels, and sub channel all have their own settings, should I disable the front crossover since my fronts have one of their own or should I set both? Also, is there a different way I should set the rear crossover (or use it at all?) depending on if I get the matching Reference series vs the Kappas that have the built in crossover?

I understand how to wire everything so I'm not a total idiot there, but I am a straight idiot when it comes to getting good SQ. I appreciate your help