At this point we don't know your listening habit, that is, how loud, same kind of level you hear in movie theaters, or much quieter? It also depends on how far you sit, what kind of speakers you have etc. You can use an online calculator such as the one linked below to get a good idea of you power need.
http://myhometheater.homestead.com/splcalculator.html
The AVR-X4400H that you asked about, it is listed for $1,599 but some people were able to get it for $799 or less recently, as the X4500H will be out in 2-3 months.
Based on S&V bench measurements, your Pioneer is about 1.2 dB more powerful than the Denon, that is truly negligible. The LX701 uses class D amplifiers, but it should still be comparable to you 94TXH for real world use, though I am more confident with the class AB Denon.
Another option is, keep the 94TXH, depending on your 4K needs, that is to buy 4K media players that offer two HDMI outputs as well the apps you need.
The 94TXH is a powerful one, it currently rank 17 out of 38 on my AVR power output chart, right below the Elite SC-89, based on 2Ch into 8 ohms, but its 2Ch into 4 ohm output is higher than the SC-89.