Might Explorer synergize with Tournament? Given that, with Tournament around, you're probably aiming to get one or more Province(s) significantly earlier than you would otherwise? Or would you, in the absence of better $5's, simply downbuy a Tournament instead?
I am aware that if you draw Tournament, Explorer, and Province, you're going to discard your Province to get a Prize and therefore your Explorer isn't going to get you a Gold (assuming you play Explorer at all that turn). I'm not suggesting that Tournament and Explorer actually combo (well, I guess they could if you also had some type of Village, but without mega draw that's not likely to happen). By "synergize" I mean that (1) Explorer's Silver-in-hand gain ability may help bootstrap your economy to Province levels sooner/more consistently, to feed your Tournaments; and (2) Explorer helps mitigate the sting of drawing said Provinces without a Tournament in hand - if you've got Explorer in hand instead, hey, free Gold.