1. The only mod you listed that matters are the pipes. Which arent that great. All that other stuff is garbage and shouldn't be in the equation.
2. Don't worry about it keeping up or beating any other bike. All that depends a lot on the rider.
3. Either deal with the less than modern suspension or look into a bike with better supspension. Afetrmarket Banshee or newer 450. Stock suspension is fine.
4. Banshees prefer open terrain. Trails? Guys on here will give you the goods on that. My experience is that they suck. So do trails for that matter. thank God I have Glamis!
5. Being an '01, it should NOT be on a stock top end. My '02 is just about due for a replacement.
2500 seems pretty cheap. Might be a great deal. But for a bit more, you can find a newer, better Banshee.