I have a 250 w rms sub and 2 x 6x9 speakers at 60w rms each
what rms value should i look for in an amp? that will be able to power the sub and the speakers

 

go with a 400 x4 .. Bridged at 2Ohms should be approx 200-250w RMS and your other two channels will be approximately 50-75 RMS at 4 ohms.

On the low end MB Quart REF4.50 400W RMS Reference Series 4-Channel Amplifier
On the mid range JL Audio XD400/4 (XD400-4) 4-Channel Class D XD Car Amplifier
Or go nuts and buy Audison or a high end ID Max amp... or whatever else..

I cant think straight. Bed time for me.