If it were me I'd get a GS300/400. Many can still be found with low-ish miles and in great shape. Your looking at a 2JZGE, or UZFE V8 for the 400. Both are belt engines, but the 2JZ doesn't even "require" a belt from what I've seen. I'd still replace it at every 80k-100k. Mine on my 1JZ was original to the engine and still looked to be in great shape.
Anyways, more on point, I think you would enjoy the size of a GS400 coupled with the power and smoothness it will provide as well.
I love the look of the Is250's but they are still a little pricey for what they are IMO.