Totally agree with Greg's comments. To flip the coin, I recently picked up a Sunn 1500S head, (orginally marketed for guitar) to use as a bass amp. The only difference between the 2000S and the 1500S (or the 'non-effect' version of the 1200S) is the preamp circuit voicing and bass boost switch.
The beauty of all these vintage Sunn amps is their ultra-linear design. They are ironically ideal for today's world of outboard effects processing and 'modeling'.
The 2000S will kick the crap out of anything new on the market but you will need to add outboard effects (pedals, rack mount, whatever), effectively using the Sunn head as your 'power amp', especially if you're after distortion effects. If your thing is low end response with the alternative tunings, you might consider at least one closed back cabinet or even throwing in a 15 speaker cab to the mix as well.
You also might want to look at the tubes currently in the amp. If 6550's of the straight sided variety, you might consider upgrading to Tung Sol 6550's (ST style) or KT-88's, either of which (to my ear) are more musical to me.
When your band mates cower in fear of the awesome sight of the massive 2000S, just tell them it's not about volume, it's about tone.