Load Balancing/Fail Over

I have 2 physical servers. I want set up asterisk load balancing and fail over solution.
I’ve examined some scenarios using products OpenSER(Kamailio,OpenSIPs), LINUX-HA, DRBD, DUNDi, Asterisk Realtime …
but can’t figure out best suit for me…
What wil be you favorite solution?
(1000-2000 users, only SIP, no voicemail, no recordings,no transcoding.)

Best Regards kajana.