Here's a review I did between the WT405 and the GK Fusion 550:
So I've tested these side by side for a few days now and figured I'd throw out a quick comparison. I will go over the power, features, and tone, as well as build quality.
Build Quality: Advantage GK
For me the GK wins in build quality and feel. The GK is solid as a rock, no loose parts or rattling inside. It's not really a fair comparison though as the Eden is about 3 years old and has been demoed during that time, but it did come with one of the screws that held the heat sink inside the amp in place rattling around inside the box.
The Eden doesn't feel cheap by any means though, it's solid, no rattling or noises when moved, the knobs move smoothly and feel very nice. The GK just "feels" more solid to me for some reason.
Features: Advantage Eden
They are pretty comparable here. Both have active passive switches, bass and treble boosts and mid shift knobs/buttons. The GK has the motorized knobs, which are a cool novelty but I could do without them. The Eden pulls ahead though because it has a headphone out and a pretty cool warm button which adds a nice amount of dirt into your signal. I do like that the GK has a footswitchable mute and channel switching though. The Eden also pulls ahead because it can do 2 ohms and it has a really really nice onboard compressor.
So at 8 ohms the GK puts out 350 watts and the Eden puts out 250. At 4 ohms the GK puts out 500 and the Eden puts out 405. The Eden does 605 at 2 ohms. Now I've always said that Eden's are a bit underpowered compared to their ratings and I still find it fairly accurate.. Although there is only 100 watts separating them, the GK is noticeable louder than the Eden. Not to say that the Eden is weak, it isn't, but the GK seems louder. It could be due to the way the amps are EQ'd, as the Eden is thick and midrangey, and the GK is really clean and cutting.
Tone: Advantage Eden
Tone is purely subjective but to me the Eden is simply better. The EQ is better, the tone is fatter, thicker, and more aggressive, and the slap tone is amazing. I've said before that the GK is a cross between Eden and GK and I find that to be true when I A/b'd them. The GK is really really clean with a bit of a mid bite and when set flat I found it to be harsh, especially the highs. I am really not a fan of highs and I've always had trouble with amps in this department. When I EQ the GK I can get a nice warm clean tone using the contour, or I could make it really aggressive by shifting the mid frequencies and boosting a bit of the low-mid. It's a great EQ, very usable and pretty flexible. I don't think either one of these amps can emulate the other.
As far as the Eden goes, when I turned it on and started playing my tone was there. Pure and simple I don't really have to do anything. In my testing I have boosted the mid knob by a couple clicks and cut the treble knob a couple clicks and that's it. The warmth button is a great little button that adds some nice grit, and even some OD depending on how you set it. Surprising enough it's actually really nice sounding. I don't think i've ever heard a SS head produce pleasing OD but the Eden does.
Both of these heads are built well, they both sound great, and they both have their own unique feature set that people look for. The customer service for GK is known to be excellent and I've dealt with them a couple times in the past with excellent results. and Eden CS is known to be crappy as of late, unfortunately, but I've not had any issues when I've called with questions. I have heard Eden does have a new CS person who is working hard to correct the tarnished image. With all this said, the Eden will be staying with me and the Fusion will probably end up leaving. Not because I don't want to keep the Fusion, because I do. I simply can't justify keeping two heads around and the Eden is exactly what I was looking for.
So that's it, I hope you enjoyed my review