Is it time to upgrade

I'm currently running a Sanders ESL MKII amp, McIntosh C47 preamp, Martin Logan ESLx speakers, a Cambridge Soundworks transport, and an Apple MacBook with Roon.  Everything sounds great, but I have the bug to upgrade.  Looking to get more detail and a bit more low end. 

I'm looking for suggestions to consider.  I've been considering either a McIntosh MC275 amp or a McIntosh C2600 preamp.  Haven't thought about different speakers, but I'm open.  Looking for 1 piece to upgrade that would make the most difference.

Thanks!