Corby

Well to avoid the Pitfall(s) of the Basic Math (of your finances) and Breakout of your situation on this Venture;  Might I recommend you save up and buy Gorf Arcade at the same time you buy Super Cobra Arcade and Star Castle Arcade?  The Arcade will be with you...Always!

Cobra and castle...meh! Butt one day, when I become big and strong, I'll own da Gorf! 

Hmmmm,

See,  to Me,  Star Castle was that one Dream Game above all others BITD,  If I really had to choose*  (I got it!@@!!) so...Dream realized...Now I do think I'll eventually buy Super Cobra (Why not?,  got the original BITD, when they sent the Atari version,  even though I'd ordered the ColecoVision version (True Story)) and of course GORF!

* I also really wanted Phoenix (Done) and Astro Blaster was right up there...(Playing Now on my 7800)...Plus "Space Rocks" of course...