if you already have your eyes on an A4 for the near future i’d look at a second hand minitaur and use the money you save to populate your iPad with some synths and other music related apps. not necessarily in this order:
Animoog
Nave
Thor
Cubesynth
Addictive
Sunrizer
Korg ipolysix
some people find it fiddly but i have got great results sequencing the minitaur and other stuff from theysys…and then of course when you get your a4 you will retain a track that you would have lost to bass duties and you can have at it on the moog with the cv output…