Would an extra 460 in sli help a lot in my system or will it create a bottleneck if it isn't already doing.
The specs are:
Nvidia 750i sli mobo
Intel e6850 at stock
Windows 7 64 bit
850w power supply
1 gtx 460
That CPU would certainly be a bottleneck, esp. at stock speeds. If you could overclock it that may help reduce the bottleneck some, but I have a feeling that it'll still be a bottleneck even when OCed.
On the bright side that PSU, as long as it's a good quality unit, would have enough power for two cards, so you wouldn't need a different PSU.