The Luxman 509x is rather weak compared to the Luxman m900u and the new amp (m10?). I have heard all 3. These Luxman amps are warmer that the other amps I mention later.
The CODA #16 is a great amp and even though it is 150 watts it is incredibly powerful because of the amount of current it generates. They do not come up for sale often. I heard the CH Precision top end amp in Canada last summer. It was over $100k USD. It was a tiny bit cleaner on top over the #16 but it was not an apples-to-apples comparison. I own the #16 and I feel the only thing I will get with an another uber amp is a different sonic presentation. The #16 is a tiny bit warm.
The new SimAudio Moon North Collection is a new fav of mine; I heard them a few days before I heard the CH Precision top amp. This was on a different system. There is a very unique character to this lineup. Very clean, very much like a slightly warmer Benchmark AHB2 but with more balls. The North amps are neutral.
If you want to save some cash and have something that is really good while you save up your pennies. Take a look at the new Schitt Wotan amp at $2k. It takes about 2 months of heavy playing for the top end to settle but I love this amp in my office system. It is not as good as the CODA #16, but I am not replacing it. It drives the difficult Maggies.It is slightly warm.