The 4500 is way too small for any decent surfcasting. Your other reel sounds better. Use your 12ft rod and the 4500 loaded with 6kg for some rivermouth fun for kahawai and trevally, or light line beach fishing on a calm beach.

I'm willing to bet your 13'6" has a tip almost as thick as the butt section on some of the better rods. Best advice.....find something you like that suits you within your range. If you can't afford it, try and save for it. A good rod will change your fishing experience and if you look after it (store it in its bag and wipe it down regularly) it'll last many years.