I see no one has yet mentioned the Virtual Bass Amp by Studio Devil. I own the Line 6 Gearbox bass pack, and since I got it I've used it on every bass track I've done. Last night I tried the VBA demo, and it sounded amazing right from the go. I had three synth basses stacked in a buss to which I applied VBA, and every one of them acquired greater depth and clarity.
I own a copy of Studio Devil's Virtual Guitar Amp, and it's a great tool for getting a great amped sound quickly and easily. It's like standing in front of the amp--that simple. VBA is that kind of thing--easy, quick, sounds great. Not terribly pricey either at less than $70. It's on my list. If I didn't already have Line 6 Gearbox, I would buy it today.
Regards, lightninrick