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TBF, you do have a good selection of decent 26" tyres, hell even Compass made some new huge lightweight slick that dramatically transform the bike, but might be moot on a cheap functional bike;
559 isn't exactly dead, just a smaller diameter to allow bigger tyres, such as this 559 conversion.;
The main advantage of 650b is that it allow the best of both world - tyres as big as 26", and fit in 700c road frame that usually allow up to 28mm tyres, at least to me, as my 650b randonneur bicycle have a shorter wheelbase than my 700c carbon road bike (!!) despite having 42mm tyres plus mudguard.
Using these: https://paulcomp.com/shop/components/motolite/
Cheaper alternative: http://www.ebay.co.uk/itm/PROMAX-CYCLING-BIKE-P-1-LONG-LINEAR-PULL-V-TYPE-BRAKES-108mm-/152024772555?var=&hash=item236561efcb:m:meLt6a_3Q6AW_3gvNHJHeBg
tl;dr of it is you need a brake with lots of vertical adjustment of pads. You will have a limit on tyre size as you are increasing the circumference of the wheel. Measure at chainstays and seatstays and fork before you buy tyres.