I know this is old...
I used Echo 620pw 59cc and just milled two 24" diameter poplar into 1.5" slabs (sections were 8'x24" and 10'x24"). Poplar is hardwood, but a pretty soft one, so I think anyone would be asking a lot to slab a harder hardwood without a bit more power. The middle section (thickest part) was really slow and took some elbow grease to get through, but I was able too chew through it by keeping th e chain sharp. I'm definitely a rookie at milling, but now I'm hooked and I'd like to try something bigger and see how much difference it makes. I'd like to be able to mill more in less time.
Unfortunately, I had a really bad experience with my first saw from Stihl and now have two Echo's that have been beyond great so I'd like to stick with Echo and go with their 80cc saw. My one concern is that with the Echo cs-800p seems like it's really hard to pull the starter. Anyone own one and have experience with that? I don't want to mess up my back pulling the starter. I have no problem starting the cs-620pw once decompression button is pushed, but cs-800 has no decompression button and if pulling the starter on it feels like the 620 does without the decompression button pushed, I'll have to get something else. At times it will catch like it's locked and that's no fun on the back.