I was really frustrated today.. Spraying primer with my 1.5HP big bertha compressor.. Tomorrow I want to be doing the top coat but there's no way I will chance it without finding a bigger capacity unit..

My thoughts were to go to SupaCheap and/or AutoOne and buy something a little bigger eg: A1 has a 2hp 50l tank for about $500..

My fear is whether this is going to be big enough to give me consistent spray pressure.. Anybody have any advice?

3 hp giving 16cfm will give you a good supply of air. Even on a really big job, I have found it is only just adequate when demanding the best results.