Ok, non-programmable Coffee makers could care less about waveforms, TV's Replays (I refuse to reference Tivo) VCR's DVD players and other electionic deivces including my laptop, like sine waves, the cleaner the better
Best sine wave inverters would be either Tripplite or Progressive Dynamics... Progressive Dynamics specialises in a lot of very good stuff for RV users... The company is dang near (if not) next door to another company well represented in RV stores, Marshall Brass and only about 12 miles from Tekonsha Engenering (home of one of the best brake controllers) I grew up in Tekonsha
That said.... I have a bunch of inverters, different sizes and quality... Ranging from a cigg-lighter job (75 watt) that runs the laptop just fine, even if it's not a very good sine wave, a 400 watt that can usually run my black & decker air compressor, and a killowatt I've never actually used (this one is going in the MH.
COSTCO currently has a 1500 Watt, forced air cooled, with leads, for I think $79.00 All in all, I think it's likely the best cost/benefit choice
I think I paid 60 for my KW job, no leads though, had to buy them elsewhere
NOTE, You should get the proper size fuse and hook thise up to the battery (Fuse hooks to the battery terminal) with the shortest leads you can use... Long leads reduce power, espically at 12vdc where the current in a kw inverter can easily top 100 amps