Audiobus: Use your music apps together.
What is Audiobus? — Audiobus is an award-winning music app for iPhone and iPad which lets you use your other music apps together. Chain effects on your favourite synth, run the output of apps or Audio Units into an app like GarageBand or Loopy, or select a different audio interface output for each app. Route MIDI between apps — drive a synth from a MIDI sequencer, or add an arpeggiator to your MIDI keyboard — or sync with your external MIDI gear. And control your entire setup from a MIDI controller.Download on the App Store
Audiobus is the app that makes the rest of your setup better.
OT: U-He Diva and Repro for 50% off (and also a separate bundle with effects)
I was just considering buying these 2 synths last night and, lo and behold, it was clearly meant to be! Still not cheap, but compared to the quality, it's a bargain. Be forewarned that these analog emulations can eat CPUs alive depending on you configure them and play them. But the sound.... oh, the sound.... If you use a PC as well as iOS for music, and there's any way you can scrape up the cash, these are among the best VSTs made to date.
Basically, with Repro, I don't ever see myself buying a Prophet. Diva is a bit of a chameleon, able to sound like a lot of analog synths.
All I have left to buy, separately, is Synapse Audio The Legend to get the best Moog D emulation, and then some wavetable synth like Hive2, Massive2 or Dune3, etc.