Are they worth the cost increase over straight steel knives? Looking at upgrading my 3 kife Dewalt portable planer to a 15" craftex 3hp unit, and im tired of straightening stock with my track saw, so im also looking at their 8" 3hp jointer. I first used a helical planer a couple weeks ago (grizzly 20" extreme) and it was so quiet compared to my Dewalt. I can get both craftex units with helical heads for 4200 brand new tax in, about 800 less for straight knifes. Thoughts and opinions, please and thanks!