Boy, this one has exploded since I looked at it yesterday. Some observations: autoboy, it's very unusual that a receiver offering several crossover frequencies would include 90Hz but not 80Hz.
Andrew(Murph), what you're missing in your #1 and #4 comparison is that LFE+Mains is only effective when the mains are set large; the reason they sounded the same with the mains set small is that they're exactly the same.
Many(most? all?)recent receivers don't handle the LFE channel in the way the Secrets article describes. Some have a fixed low-pass filter on it somewhere between 80-120Hz(e.g. one of mine lab tested as 3dB down at 96Hz); others(e.g.some Denons)offer a user setting such as 80, 100, 120Hz to set the low pass on LFE info; still others(some HKs that John Bridgman mentioned)use a choice of the settings for speaker crossovers as the LFE setting, or use the highest(not lowest)speaker crossover to control it. The exact frequency in the 80-120Hz area set isn't especially important since little or no actual LFE content is there. The reason given for ever setting less than the 120Hz LFE channel max is that some noise content above 80Hz may be reduced.
Generally, the frequent suggestion to set all speakers "small" with a 80Hz crossover appears to work well and no +mains to the sub(with mains "large")is necessary or advisable. Have the sub handle what it should do best(which should be at least up to 80Hz for a good sub)while lessening the lowest bass burden on the speakers and the amplifier driving them. Specific room situations such as the bass null that Tom mentioned for using a "large" mains setting to increase total bass output, might apply occasionally.
Study the manual, of course, to see if it actually clearly describes how the LFE channel is handled(good luck)or as a last resort try to contact customer service.
