System upgrade advice

"I'm considering replacing them with maybe some used speakers around $2.5k (pair) like some B&W 804s."

You'll make the problem worse doing that. Also, you're not going to solve the problem by just going out and buying something new. The whole system contributes to the problem you are having. You need to have some type of plan or goal as to where you need to end up, or you'll spend a lot of money and not fix anything.

Looking at your system, I suspect the problem may be shared between the tweeter in your speakers and you preamp. But just remember, anyone who hasn't listened to your system first hand, is guessing. You can start by connecting your CD player directly to your amp and use the volume control that Oppo gives you. Play some CD's that are giving you the most problems, and see if things get better, or worse. That will give you an idea as to what you need to do.

"As suggested, I connected my Oppo directly to the amp and found that it did make a noticeable difference. The treble was not as bad although still a tad bright. Unfortunately, I also seemed to lose a bit on the bass end. I will have to experiment so more."

It sounds like you are almost where you need to be. Try to get the system sounding as good as you can before you buy anything. Good preamps are expensive.

Start by moving your speakers a little closer to the rear wall. That should reinforce the bass. To fix the highs, try less toe in. Also, if you are listening to the speakers without the grills, put them on. If you still need more, tilt the speakers back a little. The easiest way to experiment with this is to put pennies under the front spikes on your speakers. Just go one penny at a time. If it works, remove the pennies and unscrew the front 2 spikes on each speaker until the same amount of tilt back you got with the pennies.

Keep in mind, you're only going to be able to do so much. You still have a digital source, going into a decent, but not great amp, and then to a pair of aluminium tweeters. For a high frequency problem like this, I don't have a lot of faith in fixing this by tuning the room. Other types of problems, yes. But the highs are very directional, and the sound goes from your tweeter, directly to you ear. If you can play around with it, without investing any money, by all means try it. But if the problem persists, you're going to have to change something in your system. There's no substitute for a good preamp. That said, they're expensive, and you would only be using it to achieve a band aid like effect. A preamp can't turn an aluminium tweeter into a soft dome. And for that reason, if I had to fix your problem, it would make more sense to replace the speakers. Once you start buying components in an attempt to fix other components, you have big problems when you go to upgrade. You would then need to buy components to compensate for the components that you used to compensate for the original component, that you should have gotten rid of in the first place. You don't want to go there.

"02-04-15: Mesch
I do agree with much of ZD posts, however I can’t help but believe that regardless of what you do with the rest of your system some dampening of the room via use of carpet and pad, curtains, and some acoustic panels at primary reflection points won’t improve the treble. A bare room is simply to alive IMO. You might look into ATS acoustics of Piper City, Illinois. They sell factory made acoustic panels and DIY supplies. There web site is good."

You do have a point about improving SQ with room treatments. A lot can be done to improve focus and imaging, take care of echoes, and all sorts of similar issues. If you are talking about an issue like sibilance and other HF related problems, its just so hard to deal with the problem when the frequencies are very directional and have a direct line of sight to your ears. For me personally, its a big issue. I've been working with this problem for many years and it seems like the only way deal with it is in a very direct way. And that's making changes with the gear itself.

That said, I absolutely agree that room acoustics should be looked at. Its a win/win situation. Even if you are not able to fix the HF issue, you're still going to make your system sound better. Also, to add to the end of Mesch's post, a while back, The Audio Perfectionist Journal did an article on how to make your own room treatments. Basically, the most common material used to treat acoustics are made out of fibre glass. Its a very simple process. All you need to do is buy the rectangular fibreglass panels they sell at your average home improvement store, and cover them with a fabric that matches the room. The cost is very low and they work very well. Unfortunately, I don't have the article or I would post it.