I think you’ll have a hard time bettering the Musical Surroundings Phonomena II at $800. I've heard that phono pre in a few different systems with very good cartridges, and it's quite good compared to anything near it's price point.
If it were me, I’d add that $800 mostly to the turntable and some to the cartridge. If you do around $2600 on the turntable and around $600 on the cartridge (or however you want to split it), it would open up many more possibilities to improve your system.