Silly turntable question

(The question, not the TT!)

I'm assembling a turntable setup, slowly over time.
At this point I have an SP-10 with the factory
obsidian plinth/cover. I have a new SME-V for it
that I bought about 6 years ago (I did say slowly). It's
not even set up yet, let alone having been listened to.

Now, I've gotten the idea in my head that I want a 12-inch
arm instead, the SME-312. THAT would mean selling the
obsidian plinth and buying something custom, as well as
buying the new arm.

I'm willing to admit that I must surely have some mental
quirk to want this change, untested.

Even so, I humbly ask you, what could I expect soundwise
if I followed through with this proposed upgrade ?
Subtle improvements ? How subtle ?
Or, should I just be happy with what I have ?

Speakers are DIY custom built, amps are Brystons,
listening room is way too small.

"Do you think I'll be happy ?" What a question.