If you're willing to accept "last year's tech", you can probably find a very good price now on the m3.
If you're able to hold out, you can buy a new one for "the latest and greatest".
The m4 (particularly the m4pro) may offer "a nice jump up" from the m3.
If you don't buy one "right out of the starting gate", but are willing to wait a month or two longer, I predict they'll even start coming down in price (as in, "$100 off deals")...