Hello,
For some time, Surround Sound Processors (SSP's) were far more expensive than AV Receivers.
When Onkyo released the Integra DTC 9.8 and PR-SC885, it established full featured processors at prices comparable to upper mid priced AV Receivers being priced around 1,600 Dollars initially.
These Onkyo's models offered virtually every feature and many more than SSP's which cost 4 thousand Dollars plus. In truth, many SSP's were behind in having the newest technologies compared to Receivers. Much of this was due to the incredible amount of competition between Consumer Electronics manufacturers in the realm of AV Receivers.
SSP's were primarily the domain of boutique specialist high end companies (Lexicon, Theta, Mark Levinson, Lexicon, et al) The prices for some of these SSP's were 20 thousand Dollars plus.
While sporting often amazing build quality and sound quality, they have often been behind on having the newest technology. This has been especially acute with the advent and adoption of HDMI becoming the de facto standard. With now 4 coming up on 5 revisions, these smaller companies have been lagging behind the larger mainstream companies. A good example of this is Theta's Casablanca Processor which can cost 20K plus, still has yet to come out with an HDMI 1.3 module. Room Correction software (Audyssey, MCACC, Trinnov, etc) is another area where many of these SSP's have lagged behind.
The Onkyo's really were a paradigm shift and nightmare for these high end companies. For the price of a quality receiver, they offer THX Ultra2 Certification, Audyssey MultEQ, XLR Connectors, HDMI 1.3, True HD, DTS-MA, HD Radio, Reon Video Processing, Internet Radio and much more. And measured performance comparable to units costing multiples of the high end SSP's.
Emotiva's SSP looks like it will be an excellent value and another competitor in what was a market of one. Denon is about to release an SSP based of the AVR-4310 for around 2500 Dollars as well. However, it will lack THX Certification and XLR Connectors compared to the Onkyo's.
The major advantage to using separates is in amplification. A well built 5 channel power amplifier offers power and current capabilities that simply trounce 99% of AV Receivers. In addition, there is less heat and interference when amplification stages are separated from sound and video processing.
But to me, the major advantage is in the amount of power and current from the amplifier.
Furthermore, as technology advances, you can use the same amplifier for years and perhaps decades and simply upgrade the SSP.
So to answer your question, at least with the Onkyo, you would only benefit by going with separates.
As the Emotiva SSP has not been released, I hold judgement of whether you would gain or lose. I will say it looks promising.
Cheers,
JJ