If gaming with WHDLoad is all you do then you won't need a 4000(T), 040/060 or RTG card anyway.
The Blizzard 030 in your 1200 makes your Amiga the perfect WHDLoad machine; no need to upgrade anything IMHO. A better accelarator won't make your WHDLoad experience any better; it may even make it worse as an 040/060 is less compatible than an 030.