We have implemented a warmstart database backup use WAL shipping which is due to go live next week, that gives us better resilience on the DB and the old server as a hot backup to the app server in case of problems there.
The idea is not to spend the money this year (who is?) but to see what the growth in traffic is like. Once we get through the busy period - Oct last year peaked at 28mil reqs/day, we'll then be planning for Oct 2010 and probably the load balanced approach.
FYI The new server is running Centos 5.3 64bit on 2 x Quad Core Zeons (with HT this gives 16 cores seen by the O/S), 36Gb RAM and 8 x 145Gb HDDs split into a RAID 1+0 volume for the DB and a RAID 5 vol for the O/S with one spare for hot swap.