The Hi-Points work. Don't get me wrong. But I just don't like them in the sense that it's not a gun I have a great deal of joy in owning, shooting or maintaining. Same applies to the Kel-tecs.
Beretta Storms would be truly amazing if they didn't have the clunky pseudo-thumbhole and cost a small fortune for polymer.
You're forgetting the semi-auto SMG variants - Uzi, MP5, etc.
I went with the midrange and obscenely expensive options in 9mm carbines personally: Vector Uzi and one of the extremely hard to find V89k-PDWs. Both are now NFA weapons - why I'd want to own a stick barrelled monstrosity is beyond me if I had a choice ;0
The Uzi is the cheapest fun option I handled: in the 650-900 range, you get 8 pounds of reassuring metal that delivers boring pop can accuracy past 100m. Don't let the people who tell you they can't hit a damn thing convince you - we're not talking about the open bolt slamming SMG here. Cheap magazines rock. If you want to SBR it, it's an extremely easy conversion. Cons are the awkward manual of arms and weight. The weight is subjective: it has literally zero recoil with +P+. Total package cost is under $1k with a pile of magazines, spare parts, and tax stamp if available in your area.
The MP5, well, it's an obvious choice if the cost of entry wasn't so godawful high. Converting a factory HK to SBR (SP-89 for the K, 94 for the regular MP5) isn't about the cost of the tax stamp any more - you're looking at 5k plus magazine and accessory costs and adding paddle magazine release etc. The only quality clone I ever handled was the extremely limited run of Vector guns (< 150 total), and good luck finding one these days honestly. It took me a year, and I could have bought a full auto Mac with what it ran when it was all said and done in terms of stamp, gun, accessories, and a few magazines. If cost is basically no concern, get a HK or a Vector gun. You're looking at $2500-6k here realistically, more than most are willing to spend but sometimes you gotta pay to get what you want.
You *can* cheap out (and cheap out is relative, as you're still in the $1300 area) with a Coharie/SW MP5 clone - reports are mixed on the guns and although they seem to be getting better, throwing $1300 at what may well be a U-Fix-Em wasn't my idea of fun. Coharie is allegedly making a 94 clone now without paddle release and stick barrel etc, but it's like buying a car with none of the comfortable driving amenities - if you roll the dice, roll it on the more expensive model IMO.
That said, if you're ever in the market for a HK registered autosear, the semi-MP5s aren't getting any cheaper and will make fine sear hosts if that's a future desire of yours. They're also generally available as pistols from the clone manufacturers so SBR conversion is easy and requires no amazing mechanical skills.
I haven't done photos of the gun since stamping it, here's my K-PDW before grip and stock: expensive, stupid, and fun, and paid for so I never have to think about it again ;0