How much better exactly is the H79 compared to the IN76 and DT-500. How much better is absolute black, contrast, brightness, sharpness and dark detail?

I got the DT-500 for a bit over $700 and and the IN76 for about $405 (but it needs dustblobs or something cleared first before it's useable). I'm considering buying the H79 (refurb) for $1299. Is it worth the price difference?

Isn't there known lamp issues with this model? How much are the lamps?

Thanks