I agree with Colby about the green bristle brushroll. When Kirbyloverdan boasted he had gotten a NOS green bristle brushroll & was using it in one of his Electrolux vacuums & he liked the improved performance, I was determined to track one down & try it myself. I have tried it in my Electrolux Grand Marquise powerhead, as well as my Electrolux Epic 6500SR powerhead, & found there was only minimal improvement. Installing the latest style 10-degree brushroll, however, definitely improves performance substantially.
Tom, Colby & Gary - I would agree the TriStar powerhead on the Guardian Platinum would improve performance. However, the metal hood & the added weight is only part of the reason why it cleans better. The other reason why is it doesn't use the floating height adjustment mechanism the Aerus powerheads have in the rear wheels. There is, however, a way to remove that floating height adjustment mechanism from the Aerus powerhead & make the rear wheels stationary. Remove the Shaft Cover from the back of the powerhead to gain access to the floating height adjustment mechanism. Remove it & set aside. Now, remove the 2 small wheels directly behind the brushroll. Re-install the Shaft Cover, take the 2 axles from the small wheels, put them into the rear wheels & install the wheels by pressing the axle into each notch on either side of the wheel opening. You will now have 2 stationary rear wheels, & you will find that the powerhead will dig into the carpet MUCH BETTER than before, & more specifically the powerhead won't float upwards when you push the powerhead forward & dig in when you pull back, it will dig in consistently on both forwards & backwards motions.
This can be done with virtually any Electrolux or Aerus L shaped powerhead, PN5 & onwards. If the Shaft Cover & the powerhead base do not have the notches to accomodate the axles, you will have to order new ones from Aerus to do this conversion. The part numbers & descriptions are below. Please note those prices are back from 2012, & may have increased by now.
45347: Rug Cleaner Body-PN1724. $43.99
45123: Rear Whl.Shaft Cover-Pow.Noz. $4.99
45125: Wheel Shaft-Pow.Noz. $2.99
If you want to upgrade to the 10 degree brushroll on an older powerhead, don't buy from Aerus & pay $70 dollars, Eurekavac.ca has that same brushroll for $23.99, part #62077-1. They have it since they used to make an Electrolux-style commercial upright that uses that brushroll.
Gary - If you try my suggestion to improve the performance of your Guardian Platinum powerhead & you are still not satisfied with it's performance, there is another solution you can try. My understanding is that the Guardian Platinum machine hose end is available as a separate part. If you bought the hose end, a new black Aerus Classic hose & matching black Aerus Classic electric wand set, you could make a electric hose & convert your Guardian Platinum to use another brand powerhead. I personally have the Eureka VGIII powerhead for my Electrolux Grand Marquise, I have it specifically for some thicker carpets I own that the Eureka simply grooms better than the PN6. It's the one on the page called "Rugmaster Vacuum Replacement". You will need to shorten the cord on the powerhead, & also will have to take the wand & powerhead into a vac shop & have them install a buttonlocker on the wand to make it work with the powerhead. Also, while you're at it, buy & use the Kirby 301291 belts you currently use with your Kirby Ultimate G, the treaded belts will last a bit longer & only cost a dollar or two more than the Eureka belts do, so worth it for the longer service life from the belt.
Hope this helps you get some better cleaning performance from your Guardian Platinum.
Rob
http://builtinvacuum.com/powerb.html