I went from Kmeaw 3.55 to 3.60 OFW just by choosing the update feature from the XMB. All I did was I wiped the HDD, restarted and chose update and BAM was back on PSN with one of my decks as I didn't need three CFW PS3's. I just didn't want to try 3.56 at all as some users were having trouble with that one from the start.
PS3 CECH-2501A [CFW] & CECH-3001 [OFW]/ PS2 SCPH-3901 & SCPH-7501/ PS1 SCPH-5501
Mod Cobra 4.46 v7.00 w/ E3 Flasher [CFW] & Cobra ODE 4.50 [OFW]/ Mod HDD-OSD [Phat] & Modbo 4.0 [Slim]/ Mod MM3
HDD 1tb [CFW] & 640gb [OFW]/ HDD 640gb & OPL v0.92 w/ 1.5tb SMB