Jeff: As E-Stat already mentioned, signal-to-noise ratios would be the key specs to compare in that case. However, unfortunately that isn't always so easy - or respectively one has to heed the details, in order not to compare apples to oranges.
Example NAD 1130: Signal-to-noise ratio specs look somewhat modest at the first glance, but then the 98 dB(A) for the line-ins are for a rated output level of only 0.5 V - and, similarly, the 76 dB(A) for the MM input also arent for the usual 10 mV input signal reference level and shorted inputs, but for a 5 mV signal and cartridge connected. So if you'd compare those specs to those of a pre-amp with a rated output level of 1.0 V as well as the usual 10 mV and shorted inputs in case of the MM input, you'd have to add a few dB each, as the 1130 would measure better under these conditions.
Unfortunately one is often confronted with such fine details in the realm of hifi specs. And unfortunately manufacturers often enough don't even provide sufficient details - so not rarely one can't be quite sure, whether one's actually comparing apples to apples...
Greetings from Munich!
Manfred / lini