The 2004 Legacy will be a great car to own, no doubt. I owned a 2004 Outback (H6) up until the middle of last year (it now belongs to my little brother), and it was great. Mod-wise, not so sure, as mine is an H6 and I don't know what the H4's aftermarket looks like. I have a feeling engine modifications will be limited mostly to exhaust modifications, maybe a tune. You should be more than fine with suspension/brake modifications; there's more than enough of those around to make it handle like its on rails haha.
Good luck, and welcome!
Last edited by TurboLag23; 03-30-2013 at 12:43 PM..