Do NOT hook up two 4ohm subs in parallel to that amp!
That amp is not 2ohm mono (same thing as 1ohm stereo) stable.
You WILL fry your amp. The tendancy for MTX amps to run hot due to their small size will only exaggerate the possibility.
To do it correctly, you need two 8ohm subs bridged in parallel. Your amp will see a 4ohm circuit, which is stable for mono/bridged operation.
BTW, I've got a MTX Blue Thunder Pro 502, one step below your amp. You did get a steal of a deal. It's a great amp. Did you get the birth certificate along with the amp? If you're curious, here are the ratings they spec'd off my amp at the factory (if memory serves correct):
52x2 @4ohms @12.5V
75x2 @4ohms @14.4V
100x2 @2ohms @12.5V
152x2 @2ohms @14.4V
THD = .005%
As you can see, MTX grossly underrates these amps. My brother-in-law has a Pro 1502 that greatly exceeded its ratings, spec'd at well over 400w.
------------------
'99 SVT
Silver Frost/Midnight Blue
About as stock as they come these days.
"Drop a gear and disappear..."