Saito are very good as are OS and others, but if moneys tight, there is nothing wrong with ASP, SC or magnum 4 strokes. Some of the finer points may not be as good as dearer brands but they still perform OK  and seem to have their legion of followers. Enya 4 strokes are real good too and Ken Enya himself will bend over backwards to assist with parts and supply direct from Japan although their price will depend more on the exchange rate.
 One of my most flown engines is a saito 56, and after near 10 years its been through 3 or 4 planes and countless gallons of fuel. It has had 2 gasket sets and 1 ring and is still going strong.</p>