I was in a similar spot a few years back. I've got an 036 that I absolutely love. I've put a larger drive bearing in it allowing me to run a standard spline rim, which in turn lets me run a 9 pin .325 rim, and it works great for firewood in the size that you're cutting.
Having the 036, I thought it would be nice to have a lighter saw for cleaning up small stuff. I've got an 024 now, but I'd really like to trade it off and get an 026. The 026 is a more usefull saw. Both the 036 and 024 run 18" bars with .325 chains. A touch big for the 024, but it's nice having the comon parts between them. Some would say that an 18" bar is too short for the 036, but I've found that for me this combination is an ideal firwood setup for this saw. It will out cut my big saw in anything smaller than 20". Even though I have a smaller saw, I find that I very rarely use it. At best, I take it with me as a back up when I know that I certainly won't need the big saw. I figure if I'm going to take a back up, it's just added weight so I should take the lightest thing I can.
Since you have the 361, I would bypass the 70cc class all together. If you want something that cuts like a 70cc saw, have the 361 ported by one of the builders on here. Instead, I would go straight for an 85+cc saw. Mine is an 064 with an 066 top end and a 28" bar (I will need to get a big bar for it too). The reason that I got it was 2 fold. One, I have a large (60"+) pin oak in the yard that will need to come down soon, and it was worth the $375 that I gave for the saw just so that I didnt' have to try to tackle it with my 036. The second reason is what another member already said. I cut in the winter, and I found that by the time the ground froze, the only thing left to cut were the tree trunks that were too big for any of the other guys to mess with. Most of it was still under 36", but over 20" While the 036 was able to buck it up just fine, it was slow. For the cost of another saw I can live with a little slow. However, once I got the rounds bucked, I had to use wedges to break them down into managable pieces. I noodled them too with my 036, but that took forever. It would take me 4 hours to get half a cord cut and loaded, and that was ash. I have no idea how long it was taking me to do a load of red/white oak. So basically, my big saw has become my portable log splitter. Does a fantastic job of noodling the large rounds that I can't get the truck close enough to. It's still slower than a Hyd splitter, but by the time you factor in having to manuver a large round over to the splitter, it's much more of a wash. As an added plus, now instead of having to lift a 200 lb round onto a splitter, I lift a 15 lb powerhead onto the round
Having an acutual big saw has been a lot more usefull than I ever thought it would be.
Unless you know that you're going to cut mainly big wood with a big saw, I would also pass on buying a new one. I would save the extra money and buy a good used one instead. I read a lot of guys on here saying that they love their 70cc saws for firewood, and that their 50 and 60cc saws don't get run as much. Around here, its exactly the oppisite. My 064 is only slightly heavier than a 70cc saw, and there's a HUGE PRACTICAL difference in weight between it and my 036. I'm in decent shape, and I can run my 036 all day long, but I only run the big saw when I need to. If all I had was a 70CC~90CC saw, I'd go buy a 50cc saw to run as my primairy saw. The woods I cut in was reciently logged, and over 1100 mature trees were removed, and when I say mature trees I'm talking about 36"+ oaks with some maple and beech mixed in. The tops that were left behind start out at 24" and up, and even at that, the only thing I use the big saw for is noodling and the occationl 48"+ section of trunk that the loggers left behind. 90% of the wood is cut with my 036, and 10% with the 064, but that 10% is good oak that I would otherwise have had to pass on. Good , hard oak that can be stacked for several years waiting for me to get to it in the burn rotation (I'm currenly 4 years a head, yay me!). No back at the house its a different story. I use the 064 quite a bit at the house for noodling. If I can safely lift it in the truck, it doesn't get split again. So there's plenty of large and/or knotty pcs in the stack that need to be noodled into multiple pcs before the can fit in the furnace, and that job is reserved entirely for ol' Bertha
The 024 is noticably lighter than the 036, but it's also noticably slower in everything and thus rarely gets used. The only reason I haven't traded it off for an 026 is because I still don't think I would use the 026 much either. I've cut a few loads with an 026. Their good saws, but I think it would be just like my 024 and rarely come out of its scabbard.
Just my 2 bits,
Mark
