P410 with 512 meg cache (no battery) $110 ebay (2 internal, sas 6gbps)
P800 with 512 meg cache (two batteries) $100 ebay (2 external, 2 internal sas 3gbs)
p400 with 512 meg cache (no battery) $25 ebay
lsi (megaraid) is a big turd compared to smart array i'm afraid to say.
ESX never supports intel software raid. It will see the drives as jbod.
I'd suggest a lsi 9260-4i for a small deploy - you can run a pair of ssd's with cachecade 2.0 to accelerate your sata drives. Just make sure your ssd's are faster than than your drives otherwise you will choke on linear but the hot caching feature would increase your iops greatly. It would be cool as heck if you could use 1/2 of the ssd for hot-caching and activate ssd-paging on esxi 5 with the rest of the ssd's which would let you overcommit much faster.
What i find useful is the newer flash back write cache - the super-capacitor design doesn't require battery replacement and a single battery only lasts 36 hours (new), 24 after a year, 12 hours after 2-3 years. the capacitor based rigs will last 10+ years easily.
I don't recommend sata for esxi btw. I had to use 6 RE4 in raid-10 to avoid storage vmotion timeouts due to the sucky speed compared to regular sas drives.
Remember you are leveraging more with esxi - so that battery counts that much more.