My $.02: keep the amp and preamp you have for now; spend as much of your budget as you can on good speakers. Spend as much time as you can trying out different speakers before you buy, as the the speaker is the biggest influence on sound, and sound preference is the most personal of choices.
Then build backwards from there with gear that works well with the speakers - i.e. an amp that controls bass well, etc., depending on the speakers, sources, etc.
BTW. Magnepans have amazing bass. It is not SPLs, which you can get from a subwoofer, but rather detailed, real bass sound.
The main point is, speakers are the biggest matter of preference and the most influential in the overall sound. So pick those first, all other gear being "interim," then slowly research and replace components to fit the speakers. Second most influential is source - lossless FLAC or CD being your best digital option. Then amp, then preamp.
Tweaks are a matter of managing your personality/compulsions as much as actually mattering in the sound. Some matter, many don't. YMMV.