Bj, yes an incorrect VTA angle can make the bass sound lean.
Basement, the 501 is made by Shelter in Japan. It is distributed by EIFL Japan over there and you can order it from them. The new US distributor is Axxis. Wavelength Audio used to do it, they may have some stock left.
Now, as far as the sound goes, people have different tastes on this stuff, so I will give my opinion. In my opinion, the Shelter 501 is the best cartridge under $1500. At $1500, you can get the Shelter 901 which is one of the best cartridges at any price. They are "old style" low output MC in the vein of the Koetsu, with low compliance, and not "tilted" forward in the treble like alot of todays MCs. I like the classic MC sound, and maybe others will like to modern "hot" stuff. You will need a step-up device, as the output is .4mv, and you need impedance loading capability. You need a good gimbal-bearing arm for these. If you put them in a unipivot, and they don't work well, don't complain to me about it. I have had some people tell me a unipivot will handle anything, and I don't agree.
There is a funny little story about the 501 that happened a while back. An importer decided to re-body the 501, and called it the "Crown Jewel". It cost $2695. It was reviewed by Stereophile as Class A, and one of the best carts they had heard. When some people started noticing the similarity to the 501, it came out that it was just a re-body of an $800 cartridge. The importer was embarrassed and stopped doing it. The cart came off the Class A list. But the bottom line is that the Shelter 501 is still giving that same sound quality as the $2695 Class A Crown Jewel. The magazines won't review the Shelter carts because they kill the carts that spend big money on advertising.
My upgrade path as best sound for $ is, Denon DL103($200), Shelter 501($800), Shelter 901($1500).