I have purchased from the following, and not necessarily engines:
traintrack.net filled my order for a #6 doubleslip very promptly. Wasn't cheap by the time I got it to the door, but his price out of his door was darned reasonable.
modeltrainstuff.com (really M. B. Klein) several times, always at my door within 8 days or so through CCRA.
caboosehobbies a couple of times.
Factory Direct Trains at least three times, twice for Hybrid BLI engines.
BLI's own Refurbished deals at their website....you can get some good bargains on repairs or refusals (even for damaged boxes), with full warranty.
discountrails although they were selling an Atlas Gold Fairbanks-Morse Trainmaster with DCC/sound for USD$149
, I see he has since gone mainly to a supplier of N scale.
Modellbahnott who sells Trix...got about the last GG1 not on eBay, and he was good to deal with.
canadianmodeltrains are very good, but don't expect much in the way of discounts....pretty pricey, but right down the pike with their customers.
internethobbies have been good. Note that I didn't type internettrains...they were horrid until the past 8 months or so, but I think someone got a clue there or it was bought out and now runs like a clock.
Don't overlook some of the etailers on eBay. Many hobby shops/shippers have outlets, or virtual stores and listings there. Type in your scale item you want, and look for the 'buy it now' listings. Those guys are happy to sell you something right away, and often the price is very competitive. Look for their transaction ratings, though...they should be above 98%.
I would have to say that cherrycreek and peachtree hobbies both get good reviews, as does empirenorthern. toytrainheaven never comes up on my list of places to slam. In fact, about the only place where I have seen persistently negative comments for a couple of years across the various model fora is internettrains, and I understand that is now a non-issue.
Do take 30-40 minutes of surfing, and go three or four pages into the hits that your web browser brings up for you. There are bargoons to be had if you are willing to search for them.
Crandell