I've used or played on just about every Pegasus sci-fi terrain kit/line.
Middling Kits.
-Syberclix is probably the least inspiring to me. Very low fences and the gothic windows don't visually jive with the clicks system.
-Hexagon(several kits available) is pretty good for beginners. Bigger buildings are easier to make and the clips don't look totally out of place against the angular panels. It was great for starting out, but I lost interest after a while. Mostly it gets used a greebling fodder now.
-Platformer (several Kits available) is very good looking (again very short fences...) I use quite a bit as parts in building my own terrain. Probably the best looking panels of the lot
Pretty good kits.
-Power Plant is a good kit for making a standalone piece of terrain. I worked one of these for a friend, though I did use some additional parts.
-The Technobridge is a very nice kit if you need a bridge. The ability to combine kits is great too. Someday I'll get one of these.
My favorites:
-Chemical Plant is not a great standalone kit, but it is by far my favorite kit for greebling up my buildings. Almost every piece of terrain I build has some Chemical Plant parts in it. Every gamer who builds their own terrain should have one of these kits. I'm thinking about buying another.
-Gothic Building series (Several Kits available. There are several of these and they are all great. You have to build your own roofs and floors, but these kits are quite big, extremely sturdy, and work in a variety of settings, from medieval up through grim Darky-ness.
Here's one I built
http://chicagoskirmish.blogspot.com/2014/09/terrain-cathedral-de-la-pegasus.html
All this to say, if you want something gothic, I'd recommend skipping Syberclix and picking up one of these
http://www.thewarstore.com/product43791.html
It's going to be a bit more expensive, but you'll end up with a much sturdier building that in a year you'll still want to use.
My Gothic Cathedral will be used for many years, but my old Hexagon buildings mostly sit in their boxes.
Other excellent options for infinity would be the Deadzone terrain kits. A bit modular looking but definitely a style that works well with Infinity.
Also, I've had really good experiences with the Dust Tactics "Warzone Tenements" and Quoneset hut packs. The Warzone Tenements remind me alot of the Gothic Building series except they're a bit more contemporary in style.
http://chicagoskirmish.blogspot.com/2015/01/fully-painted-dust-tactics-warzone.html
Again they're a bit more expensive than Syberclix, but not much and the results are much better.