@switchman, there are too many unknowns here for anyone to offer you solid guidance or information (e.g. dimensions of your sound room; musical tastes; speaker placement; acoustics of your sound room; etc.; etc., etc.). As such, FWIW, I offer this as general guidance:
Firstly, the MC152 is a high quality $5,000 amp. Your Paradigm 800F are $2,000 speakers. I had a pair of the original Paradigm Monitor 9 fed by a MAC MA5200. That was wonderful but the Paradigm were definitely the weak link in that pairing. Generally, with quality $5,000 amplification like that MAC, I would think in terms of quality speakers in the $7,500 on up range. Your Paradigms are holding that MAC at bay. Speakers are the business end of any sound system. No matter how wonderful any of your other components are, speakers can only deliver the goods they were designed for.
Secondly, MAC is very well known for conservatively rating their amps. So, avanti1960 makes an excellent point. Your MAC is quite likely really putting out closer to 190 watts into 8 ohms AND, with its autoformers, the same juice into 4 and 2 ohms, as well. In addition to watts, the current supply an amp has is just as important when it comes to proper speaker matching. In short, it's not all about the watts but also about the juice.
Thirdly, I'm not certain your pre-amp is a proper match for the MC152. Generally, I find pre-amp and amp stacks of the same family perform better than mixing & matching. With this in mind, you might find a MAC MA8900 or MA7200 more to your liking, sound performance-wise. My guess is, any of those would put you into, at least, 250 watts into 8, 4 and 2 ohm territory, given MAC's conservative rating reputation and the autoformers. That's some serious horsepower; enough to drive most speakers. Have you ever noticed MAC rates THD on most, if not all, their amps at 0.005%? Truth is, some of their amps' THD is almost immeasurable. Humans can't hear anything below 1%. Below that, it's not hearing, it's feeling it. If you want to consider tubes, I've spent around 4 hours of serious seat-time with the MC275 that needfreestuff mentioned (can't remember which pre-amp but that was a MAC, too) and that is one hellaciously nice sounding amp! However, a combo like that is mucho dinero!
Fourthly, my brother-in-law has spent quality time at an Audio Advice shop. He's been an audiophile for over 4 decades and knows his stuff. He tells me the store he was in didn't necessarily have their speakers set-up or placed for optimum performance. I have no reason to doubt him. Next time I go and visit him, I'm sure we'll both go visit that Audio Advice shop and I'll see & hear for myself. I'm assuming you are already aware of how to properly go about setting up critical listening sessions or demos under "controlled conditions" or as controlled as you can get them... yes? If not, this is something you should definitely familiarize yourself with in order to fairly and properly assess equipment performance. Everything will sound, at least a little and sometimes significantly different, under your own roof but a little preparation like this will help enormously in making informed decisions. Did you ask how many hours the MC152 you demoed at Audio Advice had on it (e.g. was it broken-in)?
Fifthly, MAC has some of, if not the best, resale value in the business. There are many obvious reasons for this. One option would be to live with your MC152 for a while (e.g. 100 hours, or so), let it break-in properly and see what you think then. If you still have the itch, you can always trade it in for something else. I've spent about 3 hours of serious seat-time with the Simaudio Moon 340i that mrklas mentioned (with GoldenEar Triton 2+ and Martin Logan Motion 60XTi). That is one hellaciously fine sounding integrated, IMHO! However, IMO, a move from the MC152 to the Simaudio 340i would be a sideways move, at best; not an upgrade, per se.
Lastly, all of this is somebody's opinion(s) and getting some direction or guidance like this is certainly helpful. The feedback you've received here is certainly good stuff! However, when you get right down to it, the only opinion that really matters is YOURS! Always let YOUR ears make the final decision! There are some audiophiles who, obviously, change or upgrade their equipment about as often as the seasons change; constantly chasing audio performance improvements, no matter how small or subtle, and there is certainly nothing wrong with that. If I had the time and money, I'd probably do it, too! There are also those who upgrade frequently to, at least in part, impress others and have bragging rights. As long as they are satisfying their own ears with the upgrades or improvements they're making in the process, that's OK, too, as far as I'm concerned. However, there is a lot to be said for just taking time to kick back, relax and listen to the music, as the Doobie Brothers would say, rather than constantly listening to your sound system. This "hobby", if you can call it that, can quickly become an obsession, making you lose sight of why you got into it in the first place, instead of the pleasure it should be.
ENJOY!
