Reliable engines, pretty well designed for their day (First appeared in the VS). Power limited by tune (Couldnt make more than the 5L V8 so artificially capped). They are thirsty engines, probably go ok in a lighter car like the VS but in the WHII statesman i found it a little underpowered. Personally if you cant afford the LS1 and have to go a V6, id focus more on the car rather than specifically looking for a super6.
That said, with a W2A intercooler and a tune they can be very quick/economical. In fact id say a intercooled/tuned super6 would be more economical and powerful than a stock LS1. Of course a stock LS1 with tune would be faster...
How much you looking at spending? I picked up a VY Berlina LS1 Wagon on injected LPG last year for $8k. I got it tuned and converted to manual for a daily driver and its been damn impressive... Cheap to run with plenty of power on tap. Id imagine sedan LS1s should be pretty cheap these days....