Well what bike for 4,000 is the question. With $4,000.00 into a warrior you could beat/out handle a lot of quads that you could pick up for 4K (depending on the quad). The warrior and its cousin the 400EX are still among the most reliable trail quads you can buy to date; what are you looking to do? Trail or MX?
First id get a stroker, cam, CDI, edelbrock carb, P&P, and good exhaust and intake set-up. Then id go for Wicked +2 or +3 a-arms, and a good set of Elka's. That should be most of your money. Buying a new quad is pointless, a raptor660 suspension isn't going to be as good as the warriors with all those upgrades, and banshee suspension is only slightly better than the warriors stock, and a yfz is going to cost more than 4000 for one thats in good shape.
And another thing, someone gave you the quad, and I'm assuming that would be your parents, i don't know about you but if my parents just gave me a quad id be happy with it all stock. Also don't you think buying a whole different quad would be kinda harsh toward them, i know if i were a parent and my kid just totally disregarded the quad i paid for with my hard earned money id feel pretty bad.
It is a 03 black and red they they bought brand new for me 2 years ago. If i get a new bike (which now i think im just going to mod my warrior) the warrior would become my dads again and he, and my younger brother would ride it. So the warrior would not just sit there. I just asked my dad and the reason he doesnt want me to sell it is he doesnt want me spending my money buying used **** when i have an 03 warrior bought new that we know everything about like the air filter has been cleaned reguarly and oil has been changed reguarlly
a warrior with $4000 in mods would be more impressive than a mostly stock rappy 660 or anything else in that price range. If you get a rappy 660 or yfz you will be jumping on the bandwagon with everyone else, and won't get any recognition for having a nice and unique bike. That's just the way I look at it though.