It depends how close to perfect you shell fit is. A custom liner can help, or assist, but they wont fix fundamental fit problems.
In Vancouver/Whistler there is really isnt any good boot fitters anymore. The really good guys owned their shops, made serious cash, and retired. The good employees mostly got jack of low pay, and so quit. The guys coming up now, just really dont know.
One good thing with SureFoot is they guarantee their work. So let them fit you, ideally with you current shells, get them to guarantee that one of their liners and footbed (you need to buy their foot bed to the the guarantee) will solve your problems. Then if it dont work, tell them in certain terms you are not satisfied. You will get a full refund. They honour their guarantee. The same cant be said for the others such as the former "SnowCovers". But that is when you own your shells, not so sure how accomadating they are when you buy the shells from them too...as obviously it is a much bigger loss for them to also take the shells back, the liners dont cost them much, so it is not really as big loss if that is all you are returining.
Having said that, Fynatico, seems to be doing some good work. George McKonkey of course still has a huge fan base. My experience with George thou is he is good at making boots bigger for wide feet, not so good with narrow feet. Plus you have to be able to deal with George, he is a nice guy and all....but never wrong, so if his fit isnt right, trust me, he will have a list as long as his arm why its actually your fault.