Thanks for clarifying.
I know you don't have any Paradigm speakers. I said that you seem to be committed to them and thats OK. If you like the way they sound, then go in this direction and get what sounds good to you. I'll respect that and won't discuss any other brands. Also, thank for clarifying that the Anthem your looking at is an amp and not a processor. I see you corrected your original post to the correct model number. Now it makes sense.
Now to answer your question. Speakers usually make the biggest impact so I would suggest getting the Paradigm Sig S2's and Paradigm subwoofer first. Like you said, you already have an amp - the Pioneer VSX23. The Paradigms are 8 ohm speakers and pretty efficient at 91 db. Try them with your Pioneer first and see how the system performs without an external amp. You may find everything is performing to your complete satisfaction. Good luck.
Marantz PM15S2 LE, Oppo BDP-103, Simaudio Moon 100D DAC
VPI Traveler V2 with an Ortofon Rondo Blue and Simaudio Moon 110LP, Technics SL-1400 with an Audio Technica AT-14sa and Pro-ject Phono Box S
Dynaudio Focus 260's, Rel T-1 and a Panasonic TC-P54S1.