I would confirm what ADTG said above and I emphasize than you better skimp a bit on the avr and add more budget into new Sub. STF1 is nice sub , but not nearly enough for 20x13 (plus open to other rooms?) space
X3000 Amazon warehouse deals still has most of x4000 features and would probably be sufficient for you.
remember it's not the electronics, but the speakers is what makes 90% difference on sound quality.