The TK800 does not feature an extra lamp, but the one included does have a rating of 4000 hours on full lamp mode and 15000 hours on smart eco mode, which is more than decent as far as projectors go. Yes, the HT2550 may be offering slightly better lamp hours but considering how much brighter the TK800 is, the numbers are more than justified.
Coming to the actual performance, the BenQ TK800 performs very well in both dark and brightly lit conditions. While its common practice to use projectors in as dark a room as possible, the TK800 has the capability to give you a powerful output even in decently lit conditions. One recommendation is that you should definitely try the TK800 in completely dark conditions because the image output is absolutely gorgeous. Yes, there are some slight nags like sporadic colour bleeding near the edges, a problem that was found in the HT2550 as well, and BenQ could possibly work on that front for their next iteration. However, at a $1500 price point, these things are acceptable considering how the pros overshadow the cons.
