Not a comparable stihl in the price range. You would have to pay more to get a Stihl that comparesto the 6100 or 620.
The 6100 and 620 are very comparable. I like the 6100 better because the AV is a bit better, and the air filtration is better. I also really like the easy starting of the 6100 and the fuel milage. All of those are subjective. I have a tore up shoulder and artists in my hands so every little bit is noticeable to me where others it may never bother. In reality most pro grade saws are excellent and you are buying which one fits your needs best and best dealer can be a big part of the buying process.
With all that said I still think for what you have described for cutting a 590 would not be a bad choice. A 6100 and 620 would be more fun. Lol
The AV on the 600 series Echo's is excellent. I agree with you that the air filtration on your 6100 is a better quality setup than the 590/600/620. But I've not had any problems with the air filtration doing it's job on the Echo's. They seem to work just fine.
I've been saying for a while now that I was going to start doing some comparison vids between the Echo's. Well, I just did a good comparison between my ported 600p and my mostly stock 620p (deflector cut out/tab deleted). The 620p got it's butt kicked by the 600p (which I expected). Cutting a 23" pine log at 6500 feet elevation and both saws using the same 24" b&c: The 600p averaged 23.7 seconds per cut vs. the 620p's 28 second average. And here's something that might surprise some people: In the same 23" log, my ported 500p (20" b&c) was only five seconds slower than the 620p (33 seconds).
I bought the 600p brand new off Ebay for $400. For that price, porting is easier to justify. To say I'm impressed with the 600p is an understatement. I bucked 15, 30" Red Fir rounds today before leaving camp with that saw. It isn't broke in yet but I'm still amazed at how it cuts and the almost instant throttle response. For a total cost of less than a 562xp, it will hand the Husky it's butt all day long (bucking). Yes, it's not fair to compare a ported saw to a non ported. The point is, when comparing the power vs. price ratio, the 562xp falls short because of it's higher price.
If the 590's performance is anything like the 600p's, it would be hard to pass up at the prices they sell for. I don't think there's much difference (performance wise) between the two from the research I've done. I just watched Andre's vid comparing his MM'd & tuned 590 vs. his stock 562xp. The 562 cut faster but not by much and the 590 is a home owner saw!