I have gone through bi-wiring, passive bi-amping and active-biamping with my equipment, which was designed to be upgraded in this way. Based on my experience, and on what you said, here are my somewhat rambling thoughts.
You state that you want more power for bass as you will not have a sub. Bi-wiring has nothing to do with this. Bi-amping or single amping with a bigger amp will do what you want.
However, before you start spending money, make sure that your present amp is not up to the job. The Mirage speakers are quite efficient, and 70 watts is within their recommended range. You may find that they are fine and you don't need to spend anything. You can save your money for some other upgrade in the future ..... or buy your wife something. Think of the sports analogy of trading a player for "future considerations". Or maybe you can buy a nice looking new rack with high WAF ..... and more rack space for those future considerations.
Anyway, make sure you need more power before you open yuor wallet.
If you do want to upgrade, bi-wiring doesn't give you more power. It simply helps to separate the high and low frequencies a little bit. So it's not your current objective. But, I have found that bi-wiring is a cost effective upgrade if you use modest cables. And I have found bi-wiring to be effective in my system with very inexpensive cables. It produced a slight, but noticeable, increase in clarity. So, I think bi-wiring is worth doing, even though it's not your primary objective. And you can do it with any amps you use. It doesn't have to be only with the amp in your second option.
Next step up is bi-amping. If your speakers need the extra power, and you haven't determined that with certainty yet, then bi-amping is an option. But then again, so is single amping with a better amp (bi-wired or not). A good single amp is better than two poor amps in bi-amping configuration. Personally, I have not found passive bi-amping to be a cost effective upgrade if you don't really need the extra power. I only recommend it as an intermediary step to active bi-amping. Now that's an upgrade!
So, in conclusion, don't spend on another amp until you are sure you need more power. Save for a more significant upgrade.
In any event, bi-wire. It's cheap and easy to do and should produce an improvement.
If you need more power, and funds are limited, consider single amping rather than bi-amping. It's better to have the limited money in one good amp rather than spread it over two mediocre ones, plus interconnects.
I can't comment on the merits of the particular models/brands you are proposing. However, there is an important point to keep in mind. If you bi-amp with dissimilar amps, they have to have the same gain. So options 3 and 4 may not be feasible depending on the gain. Option 1 would be a good choice though.
You state that you want more power for bass as you will not have a sub. Bi-wiring has nothing to do with this. Bi-amping or single amping with a bigger amp will do what you want.
However, before you start spending money, make sure that your present amp is not up to the job. The Mirage speakers are quite efficient, and 70 watts is within their recommended range. You may find that they are fine and you don't need to spend anything. You can save your money for some other upgrade in the future ..... or buy your wife something. Think of the sports analogy of trading a player for "future considerations". Or maybe you can buy a nice looking new rack with high WAF ..... and more rack space for those future considerations.
Anyway, make sure you need more power before you open yuor wallet.
If you do want to upgrade, bi-wiring doesn't give you more power. It simply helps to separate the high and low frequencies a little bit. So it's not your current objective. But, I have found that bi-wiring is a cost effective upgrade if you use modest cables. And I have found bi-wiring to be effective in my system with very inexpensive cables. It produced a slight, but noticeable, increase in clarity. So, I think bi-wiring is worth doing, even though it's not your primary objective. And you can do it with any amps you use. It doesn't have to be only with the amp in your second option.
Next step up is bi-amping. If your speakers need the extra power, and you haven't determined that with certainty yet, then bi-amping is an option. But then again, so is single amping with a better amp (bi-wired or not). A good single amp is better than two poor amps in bi-amping configuration. Personally, I have not found passive bi-amping to be a cost effective upgrade if you don't really need the extra power. I only recommend it as an intermediary step to active bi-amping. Now that's an upgrade!
So, in conclusion, don't spend on another amp until you are sure you need more power. Save for a more significant upgrade.
In any event, bi-wire. It's cheap and easy to do and should produce an improvement.
If you need more power, and funds are limited, consider single amping rather than bi-amping. It's better to have the limited money in one good amp rather than spread it over two mediocre ones, plus interconnects.
I can't comment on the merits of the particular models/brands you are proposing. However, there is an important point to keep in mind. If you bi-amp with dissimilar amps, they have to have the same gain. So options 3 and 4 may not be feasible depending on the gain. Option 1 would be a good choice though.