The textbooks used in TW that are NT300-800 in TW are often available on Amazon, but usually for 60-80 USD. I have used neither of the texts you mentioned but they look acceptable from the “look inside” on whichever Taiwanese book distributor’s site I looked at them on in the past.
What’s your end goal? If you’re looking for more level-appropriate language input as opposed to a specific grammar breakdown, I’ve used The Chairman’s Bao (https://www.thechairmansbao.com/) in the past. It’s excellent for level-appropriate input (by HSK level, through HSK 6+) and has vocabulary and grammar targets, but it covers a wide range of topics instead of dialogues that talk in stupid ways just to emphasize a grammar pattern. The audio speed is also originally recorded for the appropriate speed at that HSK level, but there’s a speed-up and slow down feature if you need it. You can hover over (on the web) or tap (phone app) words you don’t know for definition of any and all words and you can add them to a personal flashcard(s) “stack” for later review. (They have a flashcard review system on the site)
ChinesePod also comes to mind but man do their hosts, especially the American ones, think the world is made up of only China, which is the best country in the whole wide world, and America, which is full of lazy, stupid people with a backwards culture. (it’s possible that changed when they moved from Beijing to Taipei.) But sometimes they have USD$0.99 sales for a premium month subscription, and their actual software and language input is not bad. The America-bashing was strong with that one though, and that’s not necessary when you’re paying to learn a language.
Personally, I think textbooks are only good until you’re at a lower intermediate level, especially in Chinese. There’s not much grammar that you need to “learn” if you just learn the way to say the things (which isn’t as true of many other languages). You need serious and constant input and it needs to be input that you’re interested in to learn a language. If you plan to go through a lot of Chinese textbooks at once, especially at their cost from outside TW, I’d look into a leveled reader website. The Taiwanese would have you thinking otherwise, but one does not learn language by memorizing/practicing grammar patterns + route vocabulary memorization so you can eventually, someday, pull everything out of files on your brain. You learn it by hearing, reading, speaking and writing it.