No...Since OC tweaks are all BIOS based, switching PSU wont affect OC especially since you've picked out a decent one. Instability in such a case will only result if the psu cannot meet the power required in the OC'ed set up. simply put, it is safe to go for a higher power or equally powered new psu compared to your existing one if your are not sure of the system's power draw.
Ok cool thanks for the info.
Funny thing is I bought the tx750m for like $70 bucks but then just now bought a cooler master hybrid silent pro 850w for $150 plus the $40 rebate so I couldnt pass up the deal. I'll just end up selling the tx750m for the same price i got it for.