MTX amp

[68w/sbc406]

i am looking into putting a amp into my truck and i have one MTX 4402 and here are some specs i found on line
2 Channel Amplifier
Power 12.5V
Rated Power (stereo): 50 W RMS x 2 @ 4 ohms, 2 X 100 WRMS @ 2 Ohms
Briged Power 1 X 200 RMS 4 Ohm Mono
Power 14.4V
Rated Power (stereo): 85 W RMS x 2 @ 4 ohms, 2 X 140 WRMS@ 2 Ohms
Briged Power 1 X 280 RMS 4 Ohm Mono
Frequency Response: 10 Hz-30 KHz
Crossover hi/low 85Hz defeatable
Full range RCA output
Dimensions: 9.3"L x 9.75"W x 2.1"H
yet i can get a MTX 4244 amp for cheap (specs)
4 Channel Amplifier
Power 12.5V
Rated Power (stereo): 45 W RMS x 4 @ 4 ohms, 4 X 60 WRMS @ 2 Ohms
Briged Power 2 X 120 RMS 4 Ohm Mono
Power 14.4V
Rated Power (stereo): 55 W RMS x 4 @ 4 ohms, 4 X 100 WRMS @ 2 Ohms
Briged Power 2 X 200 RMS 4 Ohm Mono
Frequency Response: 10 Hz-30 KHz
Crossover hi/low 85Hz defeatable Rear
Hi pass 85 hz fixed front
Full range RCA output
Dimensions: 11.5"L x 9.75"W x 2.1"H
i dont know alot about amps and i need help understanding. the first amp is in my gfs car and the sub will cut out for a few minutes if it is a heavy bass. i dont want a under powered amp.
thanks for any info