The Monoprice and Kicker headphones are exactly the same, even if some sites report the frequency range or other tech specs to be different. In terms of the M50 and the HP541, they are 38 and 40 ohms respectively. However, the sensitivity and other factors differ, so the volume won't be exactly the same, but similar. It is odd that you found them to be much louder than the M50, but then again, it seems many people report the same thing.
Also, one thing worth noting is that the original M50s (blue box) had more bass and more of a U curved EQ in terms of its sound reproduction. The newer ones (white box) are more balanced, but of course not yet analytically or flat. They still color the sound a good amount, but not as much as the older ones. I'm not too sure when the changed them but you can look it up and see when people reported the newer ones being manufactured. If the pair that you heard was one of the older sets, then that's probably the reason why the bass seemed so dominant. Regardless, even the new M50 has more bass than the HP541. I just wanted to make sure you were aware of the change.
Personally, I listened to the M50s (the newer ones) and I was not that impressed. They are good cans to some extent, but not as good as the hype from people makes them out to be. I prefer the sound from the AKG K272s that I heard, which can be had for under $100 in today's value so it is in a similar price range. Of course the MSRP differs greatly. There are also some other cans I heard also sounded better to me than the M50s in the same price range. The clarity and detail was decent on the M50s but I didn't think they were worth the price asked for them. The Monoprice 8323 come 2/3 the way for me, but then again, the price is $25, so bang for your buck -wise it is a steal. The M50's mids are lacking and something about the sound signature I do not particularly like at that price point. I think one great reason why they seem overrated and over recommended is that they are good for a large array of genres, but not excellent at any. On many of those threads where people ask for headphones around the $100+ range the first answer is usually M50, even if it is not particularly good for that genre. I know I said it does all genres decently well, but there are some it does better in. Also, when people describe what type of sound they like, many times it doesn't even match up to what the M50's can produce, yet it is still recommended. It's just like a pre-programmed response from many.
If one can acquire the M50s for under $60 it would be worth it, but $80-120+ is overdoing it in my opinion. It's about the value of the item. The performance over the price. If one wants something like the M50s they are better off with the Monoprice headphones for a great price and if they are willing to pay a higher price that is in the range of the m50s, they are better off with another set of cans. Again, just to reiterate, I am not saying the M50s sound really bad, they don't, but for the price, there are better options.
Edited by Ipzd123 - 9/18/13 at 6:00pm