Gentle Typhoon is definitely the way to go when it comes to fans, my personal favorite is the 1850 RPM model
regardless of how many fans you have, more radiators/bigger radiators will always help
push/pull (fans on either side of the radiator) may not be very efficient or pretty, but it also helps
Thermaltake sucks, but not in the sense that you would expect, true it isn't the best when it comes to performance, but it's performance is not as bad as some people would have you believe, the problem in your case is the cooling capacity of the cooling system being insufficient, I personally have little to say bad about the performance of the Thermaltake cooling system, in my opinion it's flaws lie in the design, not in the performance (mixed metals (corrosion), acrylic blocks (cracks), high-resistance radiators killing flow (10-pass)), what's important, when it comes to dealing with Thermaltake water cooling systems, is to avoid mixing professional water cooling components with Thermaltake components so that you don't destroy your expensive water cooling components because of corrosion from other metals in the Thermaltake system.
+1 to the guy that said radiator place inside the case is not a good place, I placed my radiator on the window, where the air is fresh, it was magic for my temperatures (and for the noise levels)
and don't forget that water cooling is just a more efficient way to transfer heat, and as a result it makes the water cooling system hotter. there is always a limit to what water can do, it's possible that in some cases it can be insufficient to handle the amount of heat that you are putting on it
one more thing: tubing size is completely out of the equation (it has no effect on cooling performance at all)