More 'Detail' needed!
PSU available, form factor, power O/P required etc etc.
The BLF188XR is the current top of the pile for.
The amp you require will have to be linear, so Class AB, so push pull.
Single ended if fine for 'Generators' as you can use class C, E or D but they're NOT linear so cant be used as an amplifier.
Sure you can use class A for an amp, great with it's theoretical 30% eff, typically 20%
Or you can use class D/E generators with theoretical 100%, typical 85-95%.
NO contest in my book...
Str.