Go ahead with some SPS assuming that your NO3 near zero and calcium and alk are near reef levels. .04 is not too bad on the phosphate. I would not get too spendy, but there are plenty that you could roll with. If you let me know what kind of lights you are rolling, I can probably suggest some. The SPS will not be ask forgiving as the LPS, but some of them are pretty hardy.
Sounds like your sand bed is handling most of the phosphate, like it should. Have you ever vacuumed your sand? I might suggest that you thoroughly clean about 25% of your visible sand on your next water change. Then, like 10% each quarter after that. Then, keep this up to where you clean the sand about every 3-4 years.
You can also clean out your fuge of any additional debris. Sump too. Use a wet vac to get the junk out if you need to. This might be enough to get you down to .01 or .02 and maybe zero.