For home use 15 watts will be enough. I’ve had a good few of the 15 watt 1x8 combos, Fender, Ampeg, Marshall and Ashdown, none of them could be used at full volume unless being extremely inconsiderate to my neighbours. My Ashdown After Eight combo also handled the low B on my 5-string ok - I should add that the Ashdown was the only one I used with a 5-string.