I've been using a Hartke 3500 since I started playing bass "properly". I love the tone of the amp, it's very flexible, and it's plenty loud. I started using it with an 8ohm Ashdown ABM 4x10 and it was plenty loud in a band scenario. Now I use it with a 4ohm Zoot 4x10 and it's even louder. The last few gigs I've had it turned up to 4 out of 10. That's competing with drums, a keyboard, a guitar and a sax.
Yes, the fan is a bit loud, mine's old so it starts off really loud and then calms down after it's been on a while. I really ought to look into replacing that.