So I decided to put theAquila Thunder Cat Reds I recently bought on my Kala U-Bass to see what I thought, Here's my review....
As I was putting them on, I noticed they felt harder than the whites - more dense - and this translated into a "tighter" sound. Plus, they actually stay more in tune as you play up the neck. For me, the Whites tended to start losing pitch by the 8th-9th fret, and by the 12th, it was at least a 1/4 tone out! The Reds have virtually eliminated this problem, so I'm very happy about that!
As I said, the tone is tighter on the Reds, whereas the Whites are softer, more rubbery, and have a definite mellower, upright tone... I'll have to play the Reds more, and break them in a bit, as they're still stretching, but I like their intonation properties, as they're much better than stock Kala strings, or the Aquila Whites.
I played through my GK150, with EQ settings straight-up, and noticed I had the Voicing Filter button pushed in... after pushing it to the Out setting, I was able to get a much warmer sound. I like 'em!
One last thing; the Red strings aren't as sticky as the Whites, but they still are a bit tacky. After trying various finger-and-fret lubes (never got into using baby powder), I've settled on using Gold Bond Ultimatum hand lotion in the small 1oz travel size. It isn't sticky, doesn't load the strings up with gunk, and doesn't dry out on your finger tips. I use it with all of my basses with no ill effects. I just put a little dab on my finger tips - left and right hand - and rub it in; it works great, especially in humid situations. I buy these at Walgreens, in their Samples section....
Hope this all helps...