Short answer - yes, you can feel and hear the difference.
Longer answer, don't restrict yourself to Selmer. In the 60's, there really wasn't much else. Now there is. (Selmers are worse, others are better...) Go to a bunch of music stores (if you live in San Jose, and you have a car, you have many options) and try a bunch of horns. You'll be able to tell, and you may end up spending much less than $4K.
Longer answer, don't restrict yourself to Selmer. In the 60's, there really wasn't much else. Now there is. (Selmers are worse, others are better...) Go to a bunch of music stores (if you live in San Jose, and you have a car, you have many options) and try a bunch of horns. You'll be able to tell, and you may end up spending much less than $4K.