Most rims will accept a wide range of tire widths. I've run 38mm tires on 19mm (outside) rims. I just had to keep enough air in them to keep them from folding over in the turns.

28s feel a LOT more cushy than 23s, and less pinch-flatty.

Get yourself a decent floor pump. I run my 25s at 100psi and I weight 150 pounds. If I were 200 lbs, I'd probably run 110 in 25s, maybe 115-120 on 23s.

My favorite bargain tires for road riding are Panaracer Stradius Sport 700c x 26mm. Comfy cheap and fit in my Pinarello.