Your alternatives are:
Vectra, Orange, Netia and depending from your location it is possible that there are some local providers.
Unfortunatelly, there is no way to know if any of the mentioned ISP will be better than UPC.
Personally I would go for Orange Supernova (their FTTH solution).
You can get speeds up to 600mbits for 110złotys or $29 per month.
And you get pretty nice router.
I would advise to sign contract for 6 months first.