I love the Ushio 20K's because of the color ... they arent overwhelmingly blue. I would personally never supplement them with a blue flourescent which just serves to create a bluer look. If I wanted a bluer look, I would have gone with bluer halides.
I usually run them with no supplements and just use actinics for dawn dusk. But 420nm super actinics supplement them well, they dont create so much a bluer look like the blue T5's rather they add the blue/violet color although the T5 actinics are bluer than the more violet T12 super actinic VHOs. But you stated that you didnt like the actinics. So, I would maybe try the fiji purple or ATI procolor. As another poster stated, two Fiji purples may be too much for your tastes, same goes for two Pro Colors or a Pro color and a fiji for that matter.
I hate the procolor but some like it so maybe worth a try. Of course, you can see if you like the additional blue you would get with the blue T5's like the ATI blue plus.
Ultimately, you have to find out for yourself and the only way to do that is to try different T5's for yourself.