What you 'need' depends on what you 'want'. I like the saturation of colors u get from the actinics. I run dual Phoenix 14k 250w hqi on my frag tanks + actinics, dual 250w 14k Hamilton moguls + actinics on my show tank, geissemen 10k 150w mogul + x4 T5 actinic (454) and daylight mix on my grow tank and XM 15k 175w (no actinics) on my qt tank. If u look up the color spectrum on the bulb u have/want to buy, you can see where the peaks are (i.e. 454nm vs 420nm) and compare that to actinics to see of they will fill a gap in your bulb's color spectrum. The bulb you have has a good balance between color and growth, which is why it is such a popular bulb. Generally 20k bulbs are heavy on color and lighter on growth while 10k are opposite, with a balance in the middle in 14k or 15k bulbs. I add the actinics and run them +1hr on either side of my halides 'cause it looks cool', that is, after all, why I have my tanks
essentially, everyones comments are opinions, you just need to find out what you like. Take a look at a few tanks in shops to see the difference and determine if that is where you want to spend your hard earned cash. Good luck,
Dan