The significance of 0V output from a regulated power supply

Consider something like this kit from Apogee. It's linear, has adjustable current limit (i.e. important) and meets your budget, as long as you can live with 3A for the time being. If you go bigger, you can get 5A but you're looking at closer to $300.

You can also keep your eyes open on online auction sites for used industrial equipment like the HP6038A (60V 10A) or the 6Instek GPC-3060D (dual 30V 6A, can be paralleled).

If your output voltages are fixed you should be able to design it with linear regulators with a minimum of voltage drop over the regulators. And 1A is not the end of the world.
A switcher would be more appropriate if you have a variable output voltage. A linear regulator which can supply 30V @ 5A, but which is set to 1V out it will have to dissipate 150W.
An SMPS is dimensioned for a certain input voltage, output voltage and current. If you would vary the output voltage its efficiency will be lower. You won't get the 90% figure manufacturers boast about over you full range, maybe more like 75 to 80%.

edit
If you want the +/-15V adjustable I'd go for the SMPS, for the dissipation reason I mentioned. You can attack the ripple with a pi-filter. A high frequency switcher (like 1.5MHz) will allow for a smaller coil.