The KM90 is smoother, quieter, and more powerful than the 55. It certainly is better suited for the tools you want, especially the sweeper.Any more than light pressure on the paddles will stall the KM55.The KM55 does work well with most of the attachments.

I guess it depends on how much you plan on using the different attachments. If not that often, then the km55 should be fine. The difference is 1hp for the km55 vs 1.27 for the km90. I have a old ryobi 775r which has 1 hp and I use the expand it attachments. You really have to rev it up to use the edger and tiller. The 4 mix engines on the stihls have more torque. If I were you, I'd go with the km90. It cost more now, but its alot better than saying I wish I bought it later on. I'm looking at getting the km90 or the fs90r and buying the different gear box attachments.

I went even further and got the KM 130. Kind of pricey at like ~389$ just for the powerhead but I don't feel like its going to be underpowered. I run the power hedge clipper, the line trimmer, a brush cutter blade and the cultivator and it runs good.

I have the KM110 power head. I only use it for hedge trimming and tree pruning with the chain saw attachment. It has plenty of power for those two uses. I would think a broom would be the hardest thing to drive with a powerhead. Personally, if I had to do it over, I would still get the KM110 or the KM130. I don't think I would go smaller. I chose the 110 because of the lighter weight when cutting hedges. I would rather be overpowered than underpowered for longer engine life, as long as you can handle the increased weight. Charles Ranheim

I first bought the km 55 with the weed whip and straight shaft edger. The km 55 in my opinion does not have enough power to drive the edger. The clutch was always falling behind and you had to stop and wait for it to quit vibrating. I exchanged the km 55 for the km 90 and there is not any comparison. The km 90 had way more than enough power. And plus the km 90 even sounds better and is alot more quiet.

Wow what ever happen to bristle push brooms ! I still have a problem with Leaf Blowers lol. Just getting Old :) .