The horse is already out of the barn, as they say.
You listen to both and report back as to which you prefer.
You listen to both and report back as to which you prefer.
Gold-plated connectors are meaningless as an indicator of quality, they are everywhere these days. A good preamp will kill an A/V receiver every time, but I'm not sure that the Adcom qualifies as a good preamp - as a tuner/preamp, it is more like a receiver than a stand-alone preamp. As the others said, you listen and make your decision.
OK, OK, I get it. Although I've been listening to music for 40+ years, I have only recently moved from the "big box" products to what you might consider entry-level audiophile gear. I do trust my ears, but I also want to benefit from the experience of others who are more familiar with separates, and higher-end audio equipment in general. Even though the Onkyo A/V receiver sounds good with my system, it didn't seem to make sense to use it as a tuner/pre-amp from what little I know about electronics. For what its worth, the published "specs" for the Adcom are slightly better than the Onkyo, but I'll post when I make the comparison.
If you want to know whether that particular Adcom is better or worse than that particular Onkyo, then you can make that determination as you have both units. It really doesn't matter what anyone else thinks.
However, if you want to know as a generality whether a receiver is better than tuner/preamp, then I think that the answer is not absolute. It depends on the particular components. Usually, the receiver is not as good, but it doesn't have to be that way. Receivers are typically built for the mass market, or the entry level audiophile market. Price is an important consideration at this level, so the manufacturers shoehorn in as much as they can so the consumer gets more for their money, so to speak. And they use cheap parts. And they have a big honking transformer that is unshielded and emitting an electrical field that is interfering with the sensitive electronic components. And there's a single power supply for all the channels.
Now if a manufacturer wants to, they could (and some do)make a receiver with separate power supplies for each channel, everthing is shielded, the preamp section is totally isolated from interference, etc., etc. In other words, it's just as good as "separates". But the price will be a lot higher. However, the market for higher priced products, i.e. the audiophile, typically doesn't want a receiver. They want separates so they can upgrade and mix and match more easily. As a result, there are not whole lot of really, really good receivers that would best good separates. It would be better than poor separates though. Being a separate doesn't mean that corners can't be cut to save money.
So, in the end it still comes down to the particular units being considered. The receiver may be better or it may not be. You decide which you prefer. Myself, I think the Adcom should be a little better than the Onkyo's preamp section. But I don't know for sure since I haven't heard them. You have them so you tell me.
A couple other points.
I don't think the place of manufacture is important. It's the ratio of quality level to price point that's important. If it's a well made product, I couldn't care less whether it was made by gnomes living beneath the mountains of Switzerland. Your "Made in the USA" product could quite possibly contain electronic chips, or other parts, made elsewhere.
There's a lot of variability in how specs are measured. It's difficult to compare them across manufacturers. Use specs as a guide but trust your ears for the final decision.
One point of your post is of high importance. You said "To my ears the system sounds excellent, but I can never seem to be satisfied." The first part of that sentence largely answers your question. The second part is characteristic of most people that take the "audiophile" view of music, which is more about a hobby focused more on comparing equipment and searching for the best set up than about listening to music. The Adcom tuner/preamp, if after careful subjective testing seems better to you than the reciever, will, within less than a year, seem like not the route to take. Rather, a higher end separate tuner and a higher end pre-amp will seem to be a better choice. This tends to go on ad infinitum. Nothing wrong with that - it's a hobby. But as to sound - you find your A/V receiver as a tuner-preamp to be excellent, "excellent" is about as good as it gets. "More excellent" is an odd term.
Keep the KEF, Arcam and the Adcom amp, they offer the most flexibility and utility regardless of which direction you go. If you decide to go with a separate home theater Preamp/Processor stay away from Onkyo or Adcom. Also, what do you want your system to be like in 1-2-3 years as new formats and media emerge and make your purchases accordingly
Somec59: Your comments hit home to me. Although I'm not as knowledgable as most who use this site, I have heard enough equipment to think the KEF speakers and the Arcam CD player are as good as I've heard anywhere (almost). Also, while others have disparaged the Adcom GFA-555, I have found it to have honest and ROBUST power, and to have the power to drive the KEFs appropriately. I hope the Adcom pre/tuner is a good match, but the consensus seems to be I probably should have shot a little higher. I'll listen to it, compare it to the Integra, and then keep the best one til I get restless again. I definitely think that in the next few years I'll want a nice pre-amp to add to my system. Are there any reasonably priced concensus top-notch pre-amps?? Thanks everyone for the advice.
OK, the verdict is in, and it wasn't even close. The Adcom GTP-500II wins hands-down. The difference was immediate and significant. I don't know why, but the Onkyo Integra was somehow "robbing" or "sapping" my power. Upon hooking the Adcom up, the clarity and the soundstage remained great, but the bass came alive. The Adcom brings the KEFs to life, and no "loudness" colouration or attenuation is necessary. Before buying the Adcom, I felt I was going to have to buy a subwoofer to realize enough bass response. I thought this was odd, what with 200 wpc (325 @ 4 ohms) on tap. With the Adcom preamp, however, the bass is full, crisp and tight. Very noticeable change. All the clarity and stereo separation I had loved with the Integra remains, but the volume and the bass response have really come alive. At least with this "Receiver vs. Preamp" challenge, the winner is clear. And considering the Adcom preamp is not particularly "high end" (original cost $700), and given that this A/V receiver was not cheap (about $800), I can only imagine the disparity increases with newer and more expensive preamps. I'm not saying my unit is comparable to a high dollar Nelson Pass amp with Wilson Audio speakers, but my set up does sound significantly better than anything I've heard at the local Tweeter chain. I think some of those who commented earlier underestimated the Adcom's quality. This thing is housed in a sturdy aluminum chassis and is quite heavy for a preamp/tuner. It utilizes two sets of rca outputs; one labeled "Lab", which bypasses all internal filters and allows the full frequency range to reach the amp, and one set labelled "Norm", which utilizes some protective features. I'm using the "Lab" outputs (both sets gold-plated), and the results are exceptional. I'm sure a lot is due to my Arcam HDCD, but I would highly recommend the Adcom GTP-500II for any budget audiophiles out there. OK, I'm satisfied for now....