Try to catch the 25X as it makes less stops. Good alternative is the 49 up to the back of Moulescomb mainly as it gets a lot less crowded than the usual Falmer buses but does mean a 10/15 minute walk to get to the Amex.
I always use the 25 and get off at the stadium not the Uni Sports Centre like most as it goes around and stops near the away end which means 10 mins longer on the bus as opposed to a 10 min walk from the centre whichever takes your fancy. The 25x is quicker but stops at the station so again a walk.
49 is an option if weather is good and you fancy a nice 10min stroll to the stadium. Less crowded than a 25 bus. If you leave Hove at 6 you will be at ground by 7:15pm latest assuming a bit of traffic.
Another option is to take the 6 to Brighton station then the train. This is probably the fastest way.