do tubes have anything to do with volume?

have an amp now that is 50wpc and its much quieter than I expected

By quieter than you expected, do you mean you must increase the preamp volume more than previously to achieve the same level?

If yes, that's nothing to be concerned with, nor is it any reflection on the quality of the amp.

Input sensitivity can be effected by tubes, but much more likely this is a difference in design, input impedance, or other factors.

i've got the preamp at about all the way up. i can blast it, but i was just wondering if things would sound louder with new tubes. the tubes are about three or fours years old.

I guess it's possible the tubes are so bad it's effecting overall gain. Did you own the amp and preamp three years ago? I ask because you say the tubes are that old.

If you have other tubes it would be an easy test.