Here's the thing with fly rods, specific to being "underpowered": It's not the fish you need the power for, it's the fly.
This thing:
Takes some snot in the rod and in the line to deliver it.
This:
...doesn't.
You can throw that spider all day with a 5 wt. Try that top fly with a 5 wt. and you'll be inventing new cuss words eleven minutes after you tie it on.
If you're after panfish and little bass, your budget is fine (get the 2nd set up though, it's better). The lines that come with those rigs will be fine.
It's only after you get nuts about the subject and start trying to catch musky and big pike on a fly that your budget takes a beating...
...that fly is 11" long...
One more thing:
The real deal with fly fishing is practice casting. Practice a lot.
Most nights, when the weather is decent up here in the frozen north, I'll spend at least fifteen minutes practice casting, and I've been at it for about 6 years.
The muscle memory you need for fly casting is a different critter from chucking gear and you need to train your body to do it via repetition.
I feel like my most productive routine is to "cast around the house".
I start in the driveway, and I work my way around the house with which ever rig I've picked for the night. That way I get all wind angles, different kinds of obstacles, get to aim for different targets on each cast. Most nights I cycle through two or three fly rigs, call it 6 wt., 8 wt. and 10 wt.
...but I'm nuts...and I like fly casting for its own sake. A well thrown cast, even on the lawn, is like a welel hit tee shot on the golf course. Makes you feel good, even if there's no fish in the grass.
PS: Wear sunglasses, and a hat when you fly fish, and when you practice. And de-barb your hooks. Sooner or later, you're gonna run a fly into the back of your head, or into your cheek. It's not an "if", it's a "when'. I don't care how careful, or how good you think you are...all it takes is gust of wind when you've started your forward cast with 60 ft. of line out....
PPS: If a skinny li'l thing like this:
can catch that fish on a fly, you can catch more panfish than you can imagine...