Could simply be a fan bearing.
As for the 8350 vs 8345 vs Sony, the pricing on the 8350 has been CHEAP ($775 - 888) recently, perhaps trying to sell off some of that "stockpiled" inventory while making room for the 8345? Sure, Epson may be running the voltage on the 8345 a tad bit lower (hence the 1800 vs 2000 lumen rating) which may extend bulb life (regardless of manufacturing issues), but you can't go wrong with either! As one stated, it's a cheap projector with a GREAT image! Try saying that about a Sony! I've had two Sony models (VPL-VW10HT 1366x768 $8,000 MSRP, and VPL-AW15 1280x720 $1,200 MSRP) both of which had great images for their time, yet the pricing of a Sony w/1920x1080 is still in the $2,500+ arena... so remember this when you consider replacing a bulb, or blow out a blob... the Epson product is a GREAT product and their customer service is trying desperately to keep those of us (however many, or few) with issues as "happy campers" when they provide a free lamp, or exchange the unit as may be the case. Cudos to Epson!