Tobie
Not sure where you are based but I would recommend a visit to a good specialist bass shop where you can try some of these out. Bass Direct in Warwick, Bass Gear in Twyford & The Bass Gallery in North London are all worth a visit.
If you don't live near one of these, no doubt someone else on here can recommend an alternative.
Personally, I use the same MarkBass 1x12 combo as Lozz with a 5 string & it handles it fine. I add a 1x12 cab for medium sized gigs and it's even better. If you go through the PA at larger venues, the combo alone will probably be enough as only you will be listening to it.