Thiel 1.5's vs, 2.2's? Any thoughts?

Neither of those speakers should present any problem for your amps to drive as such, but you should inform us of the room dimensions and listening position configuration. I own the 2.2's, and these are more extended in both directions. Any Thiel is best listened to at least 8'-9' away for proper driver integration, and they do not like being placed close to side walls (however, they do like a fairly wide L/R spread; up to 15-degrees of toe-in can help with this conflict). Lowish seated listening position height is best. Placement near the front wall for bass reinforcement is possible, although the soundscape will flatten-out somewhat. If you can accomodate those restrictions, then 1.5's would be better for smallish rooms, 2.2's for mid-sized rooms (3.6's for larger but not huge rooms, though they are tougher to drive). Do not skimp on speaker cable quality, and be aware that if you like things *really* loud, these might not be the speakers for you, due to their moderate sensitivity and driver size, and first-order crossover design. Thiels excell at focus and three-dimensionality of spatial rendering, cleanliness of transients and decays, spectral and temporal coherence across the range, and low distortion and coloration (this all means that they're very transparent to sources and recording quality, for better and for worse). Other speakers can yield better 'slam' or larger image size, and may reveal less of the flaws in recordings or partnering gear, but only the best don't sound less neutral or accurate doing so.