Troll, I agree that the 555 will handle prolly handle his needs better than a 50cc saw with a 18" 3/8 set up. Porsche has a 261 set up with a 3/8 18" set up and he says it pulls it just fine, it rained here all day yesterday and I didn't get to try it. But from my expeirence with both the 346xp and 261, in stock form imho the 261 will handle a 3/8" 18" set up much better than the 346xp.
I'll respectfully say the 346xp used to be the best, it's just outclassed in the real woods by the 261. The 261 cuts more like a 311 than a 260 after they are broke in, really duplicates the Efco 156/ John Deere CS56. It just depends if you like to have a saw with all of its power on the top end, or a saw that will pull like a freight train from the bottom end all thru the top end, if you want the best air filtration on the market, captive bar nuts, a two year warranty with the purchase of a six pack of Ultra and a product that is made in the USA, vs one made offshore. Now if you want to mod the 346xp muffler, put in an unlimited coil or send it to be modded then it becomes a real contender, but in dead stock form they are just not the saw they are hyped up to be.
But it sounds like with the OP's expectation level the OP would be better served with a 555, I sure wouldn't put a 3/8" 18" set up on a stock 346. A lowly 291 would prolly give it a spanking.