Newegg has one of the most powerful product search/filter mechanisms I've seen. It's not the best UX (could use more performance and a better multi-select mechanism, and dividing the interface into three levels of simple/advanced/power search doesn't seem ideal), but in terms of functionality, it almost always has the features I want pulled out and selectable. Search for a monitor, and you'll get options for resolution, inputs, size, etc.
In terms of raw performance, I'm impressed with the speed and presentation of https://instantdomainsearch.com/ . Instant live responsiveness improves usability significantly.
I'll second https://instantdomainsearch.com/. Despite lots of copycats and more "feature-rich" alternatives, I find myself using IDS by default because of its speed and simplicity.
In terms of raw performance, I'm impressed with the speed and presentation of https://instantdomainsearch.com/ . Instant live responsiveness improves usability significantly.