One Year With Time Capsule

[WHM]

After a year's experience with TC.. here is what I have discovered. After receiving my TC last February (2008) my first set up was as follows. The TC was connected to my cable modem then I installed an Airport Extreme downstairs to extend my wireless network and Airport Express to my printer. The TC worked as promised but my network became very slow. After reading a lot of forums and talking to the guys and girls at the local genius bar was informed that I should use the Extreme connected to the cable modem and the TC to extend the network. Called Apple Support many... many times and finally found someone who seemed like he knew his stuff. He walked me thru a manual set-up on all 3 units and for a while it worked OK. My wireless network speed was restored but eventually the TC would drop out and back-up did not work most of the time. AFTER A FEW MONTHS I TURNED TIME MACHINE OFF and did no backups at all. A few week ago I upgraded my internet to RoadRunner Turbo and my speed almost doubled. Decided to rearrange the system to get Time Machine to work again. First I did a hard reset on all units back to factory set and erased all backup from TC. TC connected back to cable modem and Extreme return downstairs as an extender. Happy to say Time Machine works PERFECT backups running exactly as advertised. BIG problem with the 7.4.1 update(Time Machine would not work and dropped internet connection daily) reverted back to 7.3.2 and again all units working. NOW... back to my original problem... without a doubt TC connected to cable modem is MUCH SLOWER THAN THE EXTREME IN THAT POSITION. I think the only way to get the speed I'm paying for is to get another Extreme and connect it to cable modem and connect TC via cable to Extreme as a back up. Any one tried this? I am looking for the best of both worlds.... fastest speed possiable and TC backups for the reason I purchased it for to begin with.