Update:
After months of replacing both my 20-5 micron sediment filter and my GAC filter for the big blues and also because of the large bathtub I'm putting in for the upstairs bathroom, I realized my current setup was not going to cut the mustard.
The gac filter only does 4gpm max and the cost and hassle of replacing it about every 2 months (sediment filter was every month) convinced me to upgrade to a Fleck 5800 LXT coconut shell carbon filter. That will give me max 15gpm and should last 2-3 years before replacing the media.
So now I've got water main => rusco 150 micron => 20 micron pleated => 5 micron pleated => fleck 5800.
I also replaced all the 3/4" pex with 1" pex and have noticed a nice increase in flow. I can also taste the difference in the water - the big blue just doesn't have enough media in it to be effective.
Thanks a ton to dittohead here on the forums for helping me out beyond the call of duty and patiently answering all of my questions!
Here are some pics:
I'm going to replace the 1" pex from the fleck with a Falcon 1" flexible hose. Will do the same for the incoming copper.
Had to run 3/4" pvc drain line about 40' around the corner of the basement into the sink.
Here's the initial backwash output from the drain.