Chevyforlife, I think you should find either a GTG in your area or find a couple members on here in your area to go out cutting with. I agree with what CoreyB said above and think it's hard to assess your needs/wants and that it's a joke all the back and forth. Guys your popularity ratings are not directly proportionate to the amount of post you have made. Even though you are all correct in many areas pride in the particular areas you are good in or have much knowledge in clouds your thinking in other areas(I'm guilty also and thus qualified to make this assessment please insert the guy poking the other one in the eye here Luke 6:41-42).
I've looked at some of your past post, and it sounds like you would benefit greatly from getting together with some other guys and learning some technics. A sharp chain on your ms170 or the echo you previously sold will have no problem with cutting the wood you are cutting(better than a 550xp with a dull chain). CoreyB gave you some great advice in regards to your 170 and getting it going as well. If you just want to upgrade to have a new toy most everyone on here can relate as the 3-5 saw plan is commonly recommended on AS.
I think a used Husky 450 for 150-200 or cheaper would exceed your needs, as it looks like you get around on craigslist and have basic knowledge of how to get a good deal
. In comparison to what you have it will rip at 3.2 (advertised hp
who knows what the torque specs are but it pulls nice in wood under 12"
lol). With a 16" bar in the hands of someone who does not operate a saw on a normal basis they wouldn't even notice if I switched it out with a 346xp or a 353. It looks the same, feels very similar and with a sharp chain will cut very close for an occasional user. Lets be real here and not flame me for saying this guys. I have owned a 346ne and loved it, and now have the 550xp, 353, and a 450. I fill them all up before I go out and cut firewood and they all get used.
The 550 kicks butt, but I hate to scratch it up when the others cut pretty much the same and don't loose a bit of value unless I burn one of them up. At the end of a day of cutting I wouldn't save more than 15min in all the cutting and when you look at the amount of cutting you do that would be more time saved than you would probably save in 5yrs. A $150-200 saw seems to be the right one. Low initial cost and it will cost nothing to own until you feel the "need" to upgrade(these saws take a big hit once used and then keep there value for a long time). If you just want a little screamer(or like stihls better) then get a deal like the ms261c Brad just posted for 400+ shipping.
If you can't control the CAD and just "need" a bigger saw I have a nice ms441c-m, just pm me. Can't believe I'm the first one in 8 pages to mention a 70cc+ saw.
Hope this is helpful and also respectful to all the arguing parties who have more knowledge and experience in a small portion of their brain than I have in my whole body/ all my yrs.