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.
Parasound 5125, Parasound 2100, Pro-ject RM 5.1SE, Dynavector 10x5, Pro-ject Phono Box S, Pro-ject Speed Box II, Arcam FMJ CD17, Pioneer Elite VSX-52, Pioneer Elite BDP-52FD, Vienna Acoustics Bach Grands, Vienna Acoustics Theatro Grand, Wharfedale Diamond 9.2s, REL T-1 & Panasonic TC-P54S1