I second the suggestion for the Amperex Medical Grade Bugle Boys. Years ago I too had a 2300 and used these tubes with great results.
Tube rolling on MacIntosh C2300
I want to try out some new tubes on my C2300 preamp. I only have one source, a DAC/Streamer and do not have a turntable. The preamp has 6 tubes of which 4 are for phono (2 MM and 2MC). Should I change the phono tubes as well or since I am not using the phono stage, it will make no difference?