I’ve had a couple of soundbars, one inc. blu-ray so although cost £350 was probably the sound quality of a £150 normal soundbar. It was very noticeable and generally an improvement however I found the bass to be intrusive and there was no way of controlling it (for example in scenes with background traffic you could barely hear the dialogue as the background rumbling overwhelmed it).
I swapped it for a £700 soundbar as I had the cash available at the time, I don’t regret it but I probably should have tried some cheaper models.
So would a £150 soundbar make a noticeable difference, yes but I would definitely only buy one at that price with either no dedicated sub-woofer or one where you can control it.
On the flip-side, you do sort of get used to cheap built-in sound, my parents don’t have a soundbar and the TV always sounds horribly tinny the first couple of hours when I visit but I soon get used to it and don’t really notice it much (same with the ridiculous colour balance they prefer, apparently it looks better to them if people are bright orange…).
In your case if you can’t try the soundbars in the shop (and compare with a similar TV built-in sound) then I would order the TV, see how it sounded to you and then if it seemed tinny enough to be annoying then order one of the others on-line so you can return it if it doesn’t make enough of a difference for the cost (in your opinion).
