First you need to share a few things:
1. What cartridge are we talking about?
2. What system did you hear it with at the shop?
3. What system do you use at home?
The dealer should obviously have told you this, but the sound of a cartridge is system dependent. This might go a long way to explain why you were impressed at the shop and less so in your own home.
There are exceptions, but it's highly unlikely that the dealer will accept a return and offer a full refund. Not immediately and certainly not after another 50 hours of break-in. If you stay underwhelmed, you might consider asking the dealer to come over and check if you installed it correctly.
1. What cartridge are we talking about?
2. What system did you hear it with at the shop?
3. What system do you use at home?
The dealer should obviously have told you this, but the sound of a cartridge is system dependent. This might go a long way to explain why you were impressed at the shop and less so in your own home.
There are exceptions, but it's highly unlikely that the dealer will accept a return and offer a full refund. Not immediately and certainly not after another 50 hours of break-in. If you stay underwhelmed, you might consider asking the dealer to come over and check if you installed it correctly.