Too powerful for a naked system?

Ok I have just run into a huge problem. The setup I have now, I think, drained my battery in my '91 Lexus LS400. I was skeptical about it in the first place but my friend told me to just go on and do it. I hooked up 2 15" Audiobahn AWIS15N's to a Lanzar 2000 watt 4-channel amp. The subs draw only 650 rms each but I bridged them together and hooked them up to one channel on the amp. I used 4 gauge wiring, RCA's and turn on wire hooked up too. I go to start my car and it doesn't turn over at all. Was this amp or system just too much for my battery to handle without a cap or an Optima battery? Should I just throw my battery on a charger or is it totally killed? I'm in desperation right now. Where was the mistake?