Upgrading your 4 ohm 410 cab to another 4 ohm 410 cab will sound different but really not much louder than you are right now (unless you get a cab containing more sensitive drivers).
Upgrading from 1 4 ohm 410 to 2 8 ohm 410's will add much more tone and volume, because you got more drivers to move more air. If you want to stay with one cab you'll probably need to be looking at cabs built with different design objectives.
Does your budget include the current cab? By that I mean do you have to sell this cab before you can but the next one? If not and you can stretch to another £100 you can get a far better 410 than the ones you mentioned, and your 800 watts wouldn't even make it break into a sweat!
You might not have bonded with the LM2 but even this amp with a second cab will sound better than with one cab on its own.
Two cabs will have a "bigger" tone and sound louder than if you simply buy a more powerful amp.
Also a 5 string bass will sound better with more speakers handling those low notes.
This is all very silly. Fender aren't trying to rip anyone off, they are trying to survive.
They are repositioning their ranges and (hopefully) addressing the issues of the past. If these are better made basses (and they'd better be or Fender is gong out of business) then they will be worth the price. If anyone doesn't want to pay US prices then they have less expensive ranges (which I hope will be better built as well) to choose from.
Of course this guy is an idiot.
I hope he doesn't buy anything made in China. To do so would be to support a nasty, vicious, totalitarian state the crushes personal freedom under foot.
The original Clapton version of After Midnight had Carl Radle on bass.
Clapton nicked Carl and the rest of the Delaney and Bonnie band when he formed Derek and the Dominos.
PS
Carl Radle was also in the Mad Dogs and Englishmen band with Joe Cocker and Leon Russell.
I regularly see guys putting far more energy into their plucking and fretting than I do. In spite of that I still can't play with an ultra low action. That's why I called it a "relatively" light technique.
I don't pull the strings hard when I pluck but I can still get some buzz if the action is too low. Which I find it can be when the bass comes back from the Gallery. The bass still feels much better after they and me have made our adjustments.
The Four10 is a sensitive cab and like all BF designs, it is very efficient but if you are too loud it's the controls on your amp and bass that are causing the problem. Your amp is running something like 250-300 watts into this cab (shame Orange don't provide the 8 ohm number). The compression could be boosting the signal, but if the amp is loud on 1 and too loud on 2 try using the pad and turning the bass volume down.
Do you like the sound of this amp through your cab? If you do then dial the volume back. The cab is good, you proved that with your Ashdown. Sounds to me like the problem is in your "new" amp. If I was dealing with this issue I'd be checking out other amps. Ones with more effective controls.
Musicians usually don't "make it". Even the very good ones.
Talented and original performers do, so just find one of those and be his best mate and right-hand man in his band for as long as it takes him to "make it".
Then don't be disappointed if you and the band are fired just before the first album is released.
Last weekend I was working with a keyboard player who was fired by his 60's - 70's Top 40 band for asking too many questions about the money. Very few bands weren't being ripped off by their management back then.
To make it in a band. . . . easy. . . . meet the right people. . . . . just when they are looking for a guy like you.
. . . . if you want to go the working musician route then learn to read, play like a demon with a technique to match. . . then meet the right people, etc
Anyone trying to play this has a bigger problem than the bass sound. . . . no Harvey Mason or Herbie Hancock.
Most of the guys who put synth bass lines on their records back then actually tour with bass guitarists.
The head liners on the big 3 day festivals in the UK and Europe, that's the likes of Bruce Springsteen etc, are on something like £450,000 a show.
There's a story that Billy Preston got $4000 a show with the Stones, which is the most they've ever paid anyone.
Another player to listen to is Nathan East, in Clapton's band for most of the last 30 years.
Also Keb Mo always has the cream of the bass playing world on his records, like Reggie McBride, Stan Sargeant, Freddy Washington and Hutch Huntchinson.