Hi Paul,
I own and use shimano 4000, 5000, 6000, 8000 and Penn slammers.
4000, 5000 are to small if you are using 12lb line and are casting too the far bank of the Thames etc. 6000 and 8000 both have the same bodies just the spool size is different, 6000 is actually heavier than 8000. Penn live...