Rock, welcome to Axiom. Since you're aiming for a "budget" system, an integrated amplifier such as the two you've mentioned isn't the way to go. These days multi-channel receivers are the cost-effective option, even if limited to only two channel use(disregarding the possibility of future expansion to better enjoy music in surround mode). I'd suggest that you consider one of the excellent quality factory refurbished receivers available(if you're in the U.S.)from Accessories4less in the $200-$300 range, such as the
Denon E400.
Yes, my experience has been that although the M22s have good bass by themselves, adequate for most music, adding a sub is desirable, and this is another reason to consider an HT receiver. A crossover is necessary to best blend the M22s and sub, and since subs have no internal full crossover it's highly desirable to have this done by the amplifying device. Neither of the units you mention has a sub output and other circuitry with this capability(the sub out on the NAD is simply a line level pre-amp).
I'll also note that you're wise to consider possible hearing damage. Above the low bass(handled by the sub if present) speaker enclosure size has no necessary relationship to sound level capability and speakers such as the M22 or smaller can easily reach damaging levels if proper care isn't taken.
