If cost isn't an issue Portra will be fine. I use it for more "urban" shooting sometimes, and on a tripod just after sunset, I love it.
Ektar is generally cheaper to come by, has a slightly smaller range, but grain is basically non-existant and it can give lovely results in more subdued light. It can give you punchy colours if you're shooting punchy-coloured things in punchy lighting, but it is no Velvia.
I've had decent results with Kodak Ultramax 400 in the past. It's a cheaper consumer film but to experiment with a new style, might be worth a shot. Kodak also has Profoto 100, which I'm no fan of.
There's a really cheap Fuji on B&H (Fujicolor 200) that I've never tried. I've shot Superia in 400 and 800 and they're just okay, but Reala 100 was my favourite of all print films recently, so if this falls in between it may be good.