If it can actually do what it says it can, it'll work fine.
The difficulty is, many PSUs can't. Some "600w" units explode at 300w.
Hence, we need to know the make/model.
That sounds more like a speaker than anything else.
If it IS the PSU, replace that thing now.
What model Tt 750w PSU is it, and how old is it?
I ask because the Tt TR2 series, excluding the 80+ Bronze units, is know for being Meh at best.
I seriously doubt it'd pay for itself.
Unless the CPU is at full load constantly it's likely idling along at 10w or less, you aren't going to drop that much on a new platform.
It stops well short of the slot: http://pro-clockers.com/images/review/thermaltake/nic%20f4/f4_30.JPG
Plenty of room, even for GPUs that have a backplate.
Now if it's a passive GPU that has a full on heatsink strapped to the rear, that might be an issue.