I don't have my Spark yet.
Here are my stupid thoughts:
1) I have a MicroCube, and while I always loved it for it's portability (I get YEARS out of set of batteries), I think I never fully appreciated what it could do. It really does have great tones from each of its settings. Not quite a "push button for Van Halen or Metallica or SRV sound", but almost. If I'd been more patient for tweaking it, I could probably get every sound I wanted out of it. And there's probably a way to use it as a head through a Powered Speaker.
What it lacks: any reasonable sort of jam/practice capability or computer interface.
2) I had an AMPLIFi 150 I got on clearance from GC. I had avoided them because they got such bad reviews, and because I had tried out 4-5 different Line6 products but couldn't stand their control interface. I finally decided to try one because it was cheap, and I was trying to find some sort of whole-house speaker system (like SONUS) but not so expensive, and the AMPLIFi's work as bluetooth speakers, too. Well, when I got it home, it was incredibly easy to tweak tones. It still suffers, somewhat, from Line6's problem of throwing too many choices at you with some variations that are too minor to warrant so many choices. I tried some of the SoundCloud downloads, but it wasn't that intuitive and didn't seem like much of an advantage. I played music through it a few times to jam, and it worked fine, but not really an advantage over playing along with a song coming from my computer.
I ended up selling it because I got a Firehawk FX through a powered FRFR speaker, mainly because the Firehawk has the same interface, more functions, better input/output options, and better Variax interoperability.
What the AMPLIFi lacked: any sort of interactive jamming or integral drum machine.
3) Digitech Trio Plus. Great at learning the chords you want to play, sounds like real instruments. Perfect for jamming to a groove, also decent for recording the basics of a song.
Can't pull a song off of the Trio Plus to build tracks around it. Some basslines you might want can't be recreated. Never figured out how to set up the cables to get the crunch guitar tone I wanted without distorting the entire sound feed, unless I used the onboard effects, which are limited.
4) Spider Jam. Typical Line6 user interface inadequacy. I got one, had it delivered, saw a SpiderIV 75 that I thought was a Spider Jam for $100 cheaper, so returned the Spider Jam to GC. When I discovered my mistake, have never felt like it was worth paying full price for one, and never found one close by used for cheap enough to get it. The learning curve to make it do the kind of stuff I wanted was just too high.
5) THR-10. Credible tones. I agree with the text printed here:
I just didn't like it, tho. I had the same problem with it as I had with the THR-100 I tried out at Atomic Music: it gets credible sounds, but it just seems sort of lifeless, or edgeless, or soulless. It's good enough, but it seemed way to difficult to get it to go extreme, to get a really inspiring guitar tone, the way I could with even the MicroCube (if I tweaked it). It was like experiencing life on Sudafed, or listening to music with the speaker in the other room. It just didn't sound *live* enough.
But I sometimes don't give gear the full shake it deserves; I give up too easy.
Looking forward to the Spark, tho. I hope I'm not disappointed.
I have the tones I need from other places, but I'm really hoping for a good jam device, that makes it easier to learn songs, play along with famous songs, and develop my own songs.
We'll see.