The ultimate upgrade from where you're at would be to have a good gunsmith put a custom barrel on it, and at the same time do a linebored cylinder matched to the barrel. Accuracy would be *killer*
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One question you need to ponder: do you want a front sight at all, or just run the Tasco?
Second, is this a Stainless gun, or blue?
If the accuracy with the current barrel is good, the cheapest solution is to chop the existing barrel, or have a gunsmith do it. Regardless of whether or not you use a factory 4.6" barrel, a custom barrel or chop what you've got, the front sight needs to be totally re-mounted regardless. If your current barrel is stainless, the job won't take very long because there's no re-blue job needed.
If it were my gun, I'd call Ashley Outdoors and get one of their revolver front sight mounts, on which you can put a small dot or large dot Tritium front sight as you prefer (the mount is dovetailed for the sight, allowing quick swaps later). This is a far superior setup to the stock front sight. That's if you even need it, as you say, you've got the Tasco.
Ah, another point: what is your barrel to cylinder gap set at? If it's huge, .007 or some such crap, the custom barrel option will fix that, or you can have the factory barrel turned in at the same time it's chopped.
Last: if you're going to do a custom barrel, you can also have a caliber conversion done at the same time. A .45 barrel will cost the same as a .44/.357/whatever, and boring the factory cylinder up to .45LC won't cost that much. The .45LC is in my opinion and that of many others the best hunting caliber for Blackhawks available.