When you put more fixodent in, are you then, "good to go" for a few hours then, with regard to speaking and communicating, eating, etc?
If you've had them relined, and it's been more than a year or two, you may benefit from a second relind.
With regard to snap in type. Prices vary considerably, contingent on which Dentist, which state you live, etc., I spoke recently with a gentleman who had his lower done with 4 implants and new snap in denture, for about $6,000. But it may be more or less where you go.
Additionally, if you live near a Dental School, they will be about half the price. Worth checking out.
And, it never hurts to ask for any Senior discounts, Military discounts, cash discount, or discounts for just about anything you can think of. Most Dentists will allow discounts for about anything - you just need to remember to ask, after they've given the final price (that's when I'd ask).