You can cut up to 36" with an 18" bar on those rare instances. IMHO tough to beat two good mid sized saws with identical bars and chains. I'd much rather have 10 sharp chains and two bars and sharpen the chains at my leisure. Longer bars rob hp from the engine and tire your back sooner.
If you find after moving to Delta you have enough use for a bigger saw then get a 70-80cc power head with a 30" bar. Plenty of places you can order powerheads on line, bars and chains. No need to come up with more saw than you need when it's easy enough to buy one when you need it.
