I've owned both and would have to say the ion is the better option for the money you spend on the spitfire you could get a second hand ion and a few ups.
Then sell your angel and get and after market board and you'll have all the features you want.
Yes Angels are better quaility, but you can go on adding to the ion its going to be around a while yet!
To go back to the analagees cd vs minidisc etc . I would say its a case of betamax vs vhs (if youre old enough to remember
) betamax was far superior but vhs was everywhere and everybody could make it under licence. so its only just dieing now.
So Ion gets my vote until you can afford a Ego or similar.