Recommendations for a good power conditioner? Do I even need one?

Good power conditioning and power cords are the foundation of a good system and will make your system sound as if you've upgraded components. 

GLHF! 

I have a PS Audio P5 and it’s a great device but going to set you back for 2.5 as much. For $800 buy a DAC as your 105 is a fine Blu-ray/Multi-Player but the weaker link in your system... not sure on your speakers. Dedicated lines with decent receptacles is a step I would do before dropping money on a power conditioner or similar device.

I don’t see where you have a Pass amp so not sure on the reference above, but with my smaller P5 I do prefer my Pass amp plugged directly into the wall with AQ NRG Edison receptacle with dedicated lines. As far as Pass saying don’t spend money on aftermarket power cords as it doesn’t make a difference is nonsense as well, as a better cord does improve their amps. Most amp manufacturers will say plug your amp directly into the wall and I agree thus far that is best, but preamps/source components can be improved upon through a similar device.
I have an Oppo 205 and use a DAC thru another device so I’m speaking on experience here and not just throwing something out there. I’d look into a DAC first or consider dedicated lines with proper hospital grade or better receptacles; that being said for $800 I’d look at an AQ Niagara 1200.

In my system, I never met a power conditioner that didn't have warts...Grey was the worst.

I'd upgrade the power cords and outlets first.
Next would be an inexpensive but you will hear the difference with the Furman PST-8. Shop around for your best price including looking at Amazon. Well under $800 but produces better results than many power conditioners costing $2000. The AQ Niagara's are also very good but cost significantly more.

I went with the simpler is better concept and parted with an old PS Audio P300, and replaced it with an almost equally old BPT power conditioner. My choice in effect stayed the same, i.e. I value the betterment that balanced power has to offer. The PS Audio regenerator was good in service, but is quite complex internally, and the BPT did much of the same thing as far as balanced power goes, and only uses a very beefy transformer plus other appropriate parts. 
 Richard Grey products do have their place in my system, yet probably in the source end of the system.