BassX BXA-4100 transistor replacement

[Mote]

Bought another amp to play with. This one is BassX BXA-4100 4 channel amplifier. Cheap chinese stuff.
It has two blown output transistors. All the other amps I have "studied" so far use npn-pnp power transistor pair as outputs. This one uses MOSFETs. Why is this useful? Cheap?
Replacing blown output transistors, source? resistors and a driver transistor? (39?? right next to R166) should be easy.
On the board there are writings that all MOSFETs should be IRFZ44Ns, that would be great because I have about 20 pcs of them.
Although board states that IRFZ44Ns should be used, all of the transistors actually are FQP50N06. Almost all solder pads for big transistors look like transistors have been replaced. Someone replaced IRFs with FQPs?
I would like to replace the blown transistors with IRFZ44Ns. FQP50N06 has a bit higher limit values than IRFZ44N, this makes me worry a bit. Maybe I should replace power supply MOSFETs with IRFs and take two FQPs from ps and replace blown outputs with them?

[Perry Babin]

For the output stage, FET/BJT makes very little difference.

I generally encourage the use of exact replacement parts but if you have the Z44s, they should work as well as the originals as long as the rail voltage doesn't exceed the voltage of the Z44s you have (some are rated for 55v, others for 60v).

[mbates14]

In that amp, since ive seen that board design in 5000 different brands, I use TIP35/36Cs. they work reasonably well, without re-biasing.

[Mote]

Thanks for replies. IRFZ44Ns are already in. So far so good, works and produces audio.
I was just confused by the writing seen on the attached photo and not finding any of that type transistors from the amp.