Su-25 IS the counter-part of A-10 and as a matter of fact a much better one, since it has no analogies in the world. While carrying the same amount of weapons it is smaller, lighter (9500kg vs. A-10's 11321kg.) and that is the mass of an emty a/c.
It has a bigger radius.
Su-25 = 1250km.
A-10 = 463-1000
Su-25 is faster (М=0.82) then A-10 (834km/h).
And you may disagree with me on this one, but Su-25 looks a hell of a lot better...
All the best!