I've been a Cubase user since the Atari days (MegaST4!). Probably the best, yet simplest MIDI sequencing app. I used to mix audio in Nuendo because back in the OS9 days, it had much better automation and comping features, but I would work in Cubase until the parts were right, render to audio, then open the project in Nuendo (they were compatible).
I flirted with Logic, it was a nightmare of counter-intuitive operation, Digital Performer (not as powerful MIDI editing), and even Pro Tools (even now, it's MIDI is clunky, but audio is the best). I guess you always love your high school sweetheart!
I have a Midex3 MIDI interface (3 independent ports), then a MOTU 2408mkII audio interface (and trust me, even on that 2001 Mac, importing 48 tracks of digital from ADAT's was a breeze) and a couple of UAD-1 cards in the PCI slots. As long as you let the cards do the heavy lifting (Reverbs, echo's, compressors, main channel strip, bus compression) there's still enough horsepower even with a 733 G4 chip (LOL) to do some decent VSTi work.
It got me through many an album...