There was a time when I was on Test Cyp alone and my numbers were up, but I didn't notice much if any significant effect. Libido - so-so, shrinkage issues, just not the amazing feelings I thought I should be having. I blamed it on E2 levels going up, but at that time I didn't have the proper E2 checks done so who knows.
Anyway, I found myself on an HCG only course for a few weeks and felt great. morning erections, libido, better mood, more libido. But my T numbers never got above 500.
So, now I am on both HCG and Test Cyp. - this combination seems the most consistent and stable. My numbers are up much higher and I feel better.