I feel your pain but I do not offer you sympathy because I have an even worse problem. You see, not only do I want one of everything cool I see, but I want every variant within that group.
For example, I can't just have an AR. I must have an SP1, an A2, an A4...then I must have an XM177 clone, an M4, an M4 flat-top, and M4's with various stocks. Then I must have 16" HBAR's and lightweights. Then I must have some with SureFire's and Aimpoints while I must have others with EO Tech's and Pentagon lights. Then of course comes the models with ACOG's and Leupold sniper scopes. That's just AR's.
Then comes AK's. I must have milled ones. I must have stamped ones. I must have those made in Russia, China, Eqypt, Romania, Bulgaria, Poland, etc. And I must have them in all sorts of variants such as .223, 7.62x39 and 5.45x39. Then I want some with wood stocks, some with KVAR stocks, etc.
I'll tell you what it is. It's a disease. And there's no cure for it as it's chronic and worsens with time. I have it so bad that there's no way I'll ever be able to afford or have room for everything I'd like to have. LOL.
So I mostly try to stay with AR and AK's so I can be as interchangeable as possible and only have to stock a few different types of ammo.