I'm sure you would probably notice a difference - you're comparing a horn-loaded Klipsch speaker to a more conventional Polk with a dome-tweeter. Just from glancing at the KSB 1.1's, the Monitor 40's may provide more bass owing to their driver complement and larger size, but how much I'm not sure; from specifications the Klipsch are rated 65-20k, while the Polk's are showing 47-20k - if you've got a subwoofer in the system it probably won't matter a whole lot either way (aside from perhaps requiring you to change the crossover value a bit), if you're using them individually it still probably won't matter a whole lot (The Monitor 40's may provide more bass, but it won't be as dramatic as just adding a subwoofer to the Klipsch speakers).
The question is, and this is where it becomes more personal, is that difference going to be a positive or a negative from your perspective?
As far as technology and build quality changing - not as much as we'd like to think.
If you can try the Monitor 40's out, either at a retailer, or if you can take them home for a week or so, you'll be better able to answer your question. I'm guessing both will be "good" though.