I started diving at an SP backed dive club, so it was all MK2/R190, and it was OK. Then I bought my 1st set, an AL Supra(Cousteau)/XL because it was on sale, but nevetheless noticed an improvement, possibly from the 1st stage, the XL being identical to the R190 for all practical purpose. Then I changed to the SP MK10/20/G250 and again noticed an improvement, likely because the 2nd stage is a better design.
I still dive the MK20/G250 and standardize the whole family on it.
So it all depends on how fussy you are: you could live happily ever after with the MK2/R190/29x/39x (more or less the same thing), which will make it a great deal. Or you'll buy another set, and the deal'll become not so great, unless you go the TEC way and recycle the old set for a pony or something.