First off, the Solo 110 is probably at least 2x oversized for your loads- a Solo 60 would do. (I live in a bigger not-so-well insulated house in MA with design temps 15-20F colder than Seattle's, and the modulated output of my system never exceeds ~38KBTU/hr, and that's when all zones are calling for heat, when somebody is taking a shower.)
Solar would almost never be cost-effective, but a drainwater heat exchanger downstream of the shower would be (if you shower rather than tub-bathe.) See: http://www.efi.org/wholesale/pdfs/power_pipe.pdf That would also eliminate any question of the a 60MBH boiler being too small. I can link you to more info on this stuff if you like. The biggest/longest/fattest that fit the available will be the most-cost-effective. They do nothing for tub-filling capacity, but you can get better than 50% return of shower use energy (which is like adding 20-30KBTU to your boiler output while showering, depending on your flow rate.) Size the indirect for your tub fills, and you're done.
Alternatively the Excellence would PROBABLY work, but you might have flow issues if you have high peak-demands for hot water. It's minimum modulation is probably 1.5-2x your heating load, but it's max might come up shy if you're trying to fill a tub and take a shower at the same time in January. My WAG would be that your design-day heat load is less than 25KBTU/hour, probably even under 20K if it's a reasonably tight house with reasonable amounts of window area, and all windows double-paned or at least fitted with storm windows.
Demand a computer generated room-by-room heat loss calc from contractor for both radiator & boiler sizing. Those that offer that offer it up without you haveing to ask move to the head of the line.
Ask them for cheapest/nicest/best for radiator types. There's quite a range out there- it need not cost an arm and a leg, but you may want nicer-looking versions in some rooms rather than purely-fucntional versions in others. Cheap fin-tube baseboard can work with condensing boilers, but the practical limit for most is ~120F water, below which it's tough to design for output. Taller or cast iron baseboards work better, but can be pretty pricey. Low-temp panel radiators are probably a better choice for most rooms.