I have heard a few ways you can mod a turbo for better graphics.
240p is as good as its going to get
Pretty much sums it up. Personally the RCA stock connects is quite acceptable and paying to get a mod for RGB is only prudent if you have a PVM or some fancy pants CRT that accepts the one true video signal (RGB/SCART).
What type of display are you using?
Back to this...if you're rocking a LCD, you going down a rabbit hole when a $5 goodwill CRT will give you what $100+ is going to achieve.
I have a Dojindance<?> RX with the S-vid and SCART mod, the s-vid IS clearer but there is a off tint that I've experienced that makes me just run composite(I mainly use it for RBG on a 13/20" PVM at cons, but at home I have a 35" that works well for my setup even tho I run composite on it). Moral is that not all A/V mods are equal.
Don't get me wrong, the obey RGB is like sex with Hendricks, but it can cost. If you're the type of guy that drops $150 for Spriggian and can afford the luxury of brilliant video, then DO ET! Other wise, keep obeying on a CRT.