Radios on Small Carriers

[ChaosTheory]

I am looking at flashing a new radio and had a few questions.

I use a small carrier, (Nex-tech wireless) and would like to dump my current radio to flash back to if needed. Is this possible?

What advantages does a new radio have over stock? Better signal and reception, or speed, or what?

Is the radio carrier important in making a decision? For example, AT&T is not very big around here (very little coverage), so would using an AT&T radio provide lower quality results than say a Verizon radio (pretty good coverage around here).

If I am not able to dump my radio and still decide to flash, what is the liklihood that my phone/carrier is not compatible with any of the available radios? I know the physical radio that actually connects to the towers can't be changed, but not sure if the software could cause issues.

And finally, any suggestions from users in Kansas (or anywhere) as to a good radio?

Thanks!