In preparation to redoing lawn, I got my soil tested from Agricultural extension. (Soil-Sandy loam, Organic c - Medium, PH - 5.4 to 5.7, Nitrate Nitrogen - Med, Am. Nitrogen - Med low, Phosphrous - Med low to Med, Potassium - Med to High, Calcium - Med to high, Magnesium - Med high to High. The report recommends adding lime and fertilizer (20-10-10 now, 25-5-10 spring)

I also feel land has hardly any top soil. One landscaping guy also mentioned the same. So I was thinking of getting 3 inch worth of top soil delivered.
Agri. extension guy felt since weeds are growing there is soil and I should try to fix it by - 1)Round up lawn 2) After two weeks mow it very low 3)Core aerate 4)Broadcast seeding 5)Thatch it to work seeds in soil. He said if I get top soil delivered i might be fighting with some other problem with that soil.

So now I am confused should I follow Agri. extension guy's advice Or 1)Round up lawn 2)Mow it short 3)Put top soil(3inch layer) and compost(1 inch layer ?)4)Roll 5)Seed using slit seeder 6)Put starter fertilizer 7)Roll 8)Water

Also if I go adding topsoil route do I need to stick to same fertilizer ratio or go with the starter ferts ? Since ultimately I would like to go organic route, should I put organic ferts now itself or stick to synth. until Lawn get established.

Partly I feel, I should not spend money on top soil if I don't have to and on other hand I feel I want to do it right this time to avoid any future pain and expenses. So please help.

Thanks.