I've used up a spool of PE-4 and will be ordering a spool of PE-5 this year. Great stuff, I prefer it to power pro and tuff line.
In reality I don't think the smaller dia makes for a significant decrease in drag over the same weight super line from other manufacturers. Let's say you've got 50# power pro on one rod, PE-4 (55# on another) and 65# power pro on a third rod. If you need an 8 oz jig for the current on one rod, you'll need it for all. If you need a 16 oz jig for one rod, you'll need it for all. That's been my experience fishing rods with those lines in the same conditions.
At those depths it might be enough of a difference to notice. I haven't seen it as a huge advantage down to 450'. Another advantage to the thinner line is you can fit alot of it on a reel. An avet sx can hold over 350m of PE-4.
Another option is spider wire. It is really thin and tough. I usually buy it off Ebay. I just purchased 1000 mm of 80lb test toro tame from Clark Bait of $99 it comes in muti color or white. I purchased 80lb in colored and 60 lb in white. I put about 1200 ft of backing plus 1500 ft of the 80lb on each of my electric reels.