get two BLs, unless you think youll be gettin bigger amps/alts/batts, stick with BLs, they'll sound great on 2000 rms. BTLs would sound good too, but it's a waste of money. You're upgrading your electrical right?
...i think it would make more sense doing 2 SSD (800wrms) since these subs r underrated & can handle more so the 2000wrms on ur amp would be better suited ...