Plinius SA-250 Mk2 vs Mk 4; Just how much better?

l was hoping there was someone on the site that has heard both versions of the SA-250 and could comment on the sonic differences between the two. l understand the design was reviewed on the mk4. l have commited to buying the mk2 and already sent the money, however l have the choice between a mk2 and 4 but the 4 is going to cost me US$1400 more.

Would it be worth it the extra $$?

Thanks for all the help from the Gon community over the past few weeks,

Simon