I can't really think of anything good to say about the stock ION XE... an upp'd ION may be different, but mine just felt cheap....
The vibe is supposedly very good, and the upgrade board, QEV and eyes are not that expensive... but then thats about it, new board, new ASA, new barrel and then you are stuck for mods.
But i would go for the Vibe Blackheart which should only just be more expensive than a new XE and it should shoot a lot better.