I run 6 10K UV brand bulbs on my 29G frag tank. No actinics. It is all personal preference though when it comes to using them on a reef tank for looks. The higher the K the more blue it will look (but less PAR output).
The reason I went with the configuration I did was because I have SPS corals in the frag tank and wanted the most light possible without going MH. On my main 75G tank I run 4 22" UV Super Actinics with a 10K 400w MH.
If you hadn't figured it out yet, with UV brand they call theirs V-HO, which stands for Variable High Output, meaning you can run them 24w or 40w (with an Icecap 660 ballast, which I do on my main reef). It is confusing because they are not in fact VHO bulbs, the (-) dash makes the difference.