Here are 2 posts I made over at TGP about the Helios/Eclipse:
I have had both the original 50 watt as well as the 100. Currently have the original 100 watt and the Eclipse.
The Helios is an exceptional amp *for what it is designed to be*. The complaints that you see from people are in wanting it to be something it is not. It is not a 2 channel amp that lets you switch from a pristine Fender/Marshall/etc clean to a high gain M style amp. It has 2 inputs that allow you 2 VERY different voicings. But they do not overlap.
Having said that, if you have played early Marshalls (original or modded), you will enjoy this amp. It is more flexible and has a greater feature set. The Plex input is just that, a Plexi style circuit. You won't get the Hot input tone from the Plex input. For my needs, Hot input, gain 2-3:00 and roll the volume down for clean. You're not going to get modern levels of gain out of the amp, regardless of the gain setting without an external boost or drive. Think 1967 - 1987.
The Eclipse addressed some of the early complaints about the Helios. It has a slightly quieter loop and and 2 dedicated gain channels along with a simple clean. Channel 2 will approximate the Helios Hot input but it is not the same. It's hotter and a bit smoother in the Hot 70's setting. The gain and compression goes up from there (80's/Eclipse settings). I find the Hot settings on channels 2/3 are plenty of gain for me. Eclipse mode is just way over the top. With the Gain control rolled down, you get closer to the Hot setting but the tone/feel is not the same. You do lose the Plex input on this amp. If you love the Plex setting from the original Helios, stick with that amp.
One other comparison - The Helios (either version) doesn't sound like a BE100 or SB50. With the Structure switch on the BE100, it is closer to the regular Helios but the Helios is still more raw.
YMMV....
Eclipse & Eclipse + add a s*^tload more gain. It still lies in the same tonal space as 70's/80's mode but is more compressed. I go for a more open sound, so I don't use them. The Eclipse mode gain down below 11:30 is somewhat workable.
The amp was a step up for me because I needed a true clean channel and a "lead" channel which the 3rd channel affords. You can use ch2 as your main rhythm and then just build on that for leads with ch3. Add the same gain levels, Ch3 in 70s will add a bit more gain and compression with the added ability to increase volume for solos. So it is a true 3 channel amp.
The noise floor on the Eclipse loop is a bit better as well. But the loop is optimized for pedal levels.