Just bought the t1w & 404, quite happy with them, but "thanks" to head-FI consider some more

staxs
so start with sr- X
I saw a lot of post about the sr-x mk3
but there is also sr-x
sr-x mk2
sr-x mk3 pro
can anybody comment on these sr-Xs?
some mentioned ,the sr-x(not sure with one) is similar to the sound of K1000?
if possible maybe compare with 404 (or lambda signature)
just want to be ready when the gears shows up in auction!
Since the not-so-good 404 sounds amazing for me , I am seeking new/old gears from stax, for that I can not spare 2000 usd for a source , my source is currently as hi-fi as i could go for the time being(just a echo mone 24) ,and the amp is good, unless the omega 1 with the t2 in a super good price range,which means I should not just go and grab a O2 ,I know the stax phones before 1994 is very much different from the current ones, but the O2 is certainly only 2nd to the O1 ,and I am not only out there for a generally better one than my current 404 , just want to collect some more characteristic staxs.
I would keep hunting for old-good stax phones (not very much into amp , that is something people could always make better)
SRĪ£ pro & the old lambda pro will be in my hunting list for sure , just won the lambda signature! still wondering if I should pick up one of sr-Xs or they are all very different(that means to buy all of them ,maybe?)
I am in Japan , which I guess makes it easier to collect them, is there any other phone I should keep an eye on?
Cheers
GearGeek