A whole ton of people are going to disagree with me, but putting an old cap like that in your SEX amp is like finding an old can of gas in someone's shed and pouring it in your car's gas tank.
If you are looking for a nice inexpensive upgrade for the .1uf interstage cap you might want to try one of these. http://www.parts-express.com/audiocap-ppt-theta-010uf-600v-film-foil-capacitor--027-710
I think it is a nice sounding "bang for the buck" replacement and a big step up from the stock brown film cap. IMHO they go together nicely with the stock Solen parafeed cap. You could spend A LOT more money for a little sonic gain. Of course YMMV.
That was fast- I just got the caps from parts express and they are already in circuit. Can't judge a cap immediately upon installation- but everything sounds good-
Running the Sex 2.1 with Beyer T1 2nd Gen at the moment-