I recently upgraded a late production VSM SE ( more similar to the MM/MX than earlier SEs ). I really liked the speakers prior to the upgrade and certainly prefer them now. All the VSMs I've heard share a very strong family sound. It's funny that you should mention Quad/Maggie because that's the family I'm thinking about. Although Quads and Maggies (and, for that matter Sound Labs, etc) sound different from one another, IMHO they share cetain sonic traits that set them apart from most dynamics.
I suspect that -to the extent you see split opinions on Merlin in these threads - it reflects the split opinion on such planars. In many ways, all VSMs sound "planar like" to me. The most recent iteration adds very "un-planar-like" (how's THAT for a word!) bass impact.
If I were trying to conserve cash, I think
1) I'd try to find the least expensive VSMs out there
2) Contact Merlin to determine ultimate upgradability (as well as any other info/issues attendant to that particular series) in the future.
3) Do the S-BAM upgrade straight away.
Best of luck with the search.
Marty