335i fanclub: unite! 
Judging by your options I see you have a budget of $10-15k. E60's are nice cruisers, spacious, but aren't too fun in corners. The 323i/323i would be my pick. 320i have some issues with burning oil, so if you find yourself inspecting one go over it well. The x23/25i will have ample power and you won't feel like you've downgraded too much. 320i will feel slow as.. you'll probably sell it within a few months after buying. Find an Msport model if your budget allows.