Matched Tubes - Is there really a big difference??

Have a few Tung-Sol 6SN7 tubes but they are not matched pairs. I own a Counterpoint power amp modified to use two 6SN7 tubes. It is a hybrid power amp, tube ins with SS output. Will I hear a big difference if the tung-sols are not a matched pair? What exactly will I hear or be missing? The matched pairs go for $350-$400 ouch.

Unless you can individually bias each power tube, matched sets will improve the overall sound simply because the tubes will be drawing similar current.
HOw close are they? IOW, how close do the tubes match triode to triode and tube to tube? In this case, these are not output tubes, but some amps (my Joule, for example) provide for biasing of small signal tubes.
The amp has one rectifier 6CA4 tube and two 6SN7 tubes - one per channel. See the links for pictures. Thanks for the assistance.

That really depends entirely upon the circuit you'd be using them in. I'm not familiar with your amp - but I might suggest you ask the manufacturer. Matched power tubes in circuits that are individually biased, for instance, won't make any difference assuming the bias is accurate and identical. Matched tubes in a parallel SET circuit wouldn't make any difference. I think they become more important in preamp circuits, but I know too little to make my speculations dangerous. Someone with more grey matter between the ears can correct me here.

As an addendum to your question - I've always wondered this - When you purchase a set of matched tubes for a circuit that actually does take advantage of the fact that they are closely you play stereo music through them, which sometimes taxes each channel slightly differently, don't the tubes become gradually mismatched according to that uneven demand on them? If so, and you start out with matched tubes, how long before they are no longer very close?