This Should Be interesting

Hi Everyone, I'm wondering if someone here can shed some light on this for me.

Im a professional musician, and a trained sound engineer with my own studio, i have a pretty good understanding of sound and how things work, but being dyslexic seriously lacking on maths side of things when it comes to working things out. 

my band has been slowly building its reputation and moving up into bigger venues, so a year half ago decided to upgrade my rig and bought a bose F1 system because of its power size and weight, it was the most powerful and smallest i could afford. i assumed that 2,000 Watt peak per side would be enough, but I've been becoming more and more disappointed with it. its maxed out most of the time to the post where its starting to clip . having to crank up the input gains and overall output to get the main vocals loud enough at the back of the rooms, its becoming a daily struggle. and of course you reach a point where the main vocal mic is that loud theres no way to stop the feedback without physically turning it down. 

i must point out were a very very loud old fashioned blues rock band, with two 1960s 100w Marshall stacks with 4x12 cabs, 1000w 8x10 and 1x15 Bass rig, Large over loud 60s drum kit..oh and the main vocalist plays harmonica into the same mic, and is constant cupping the mic in his hands tp play ( feedback nightmare ) ..  95% of the time we full the room with stage sound alone, the PA is really just used for sound reinforcement and spreading the sound, mainly gets used just for vocals , kick drum, high hat, and sometimes guitar if outdoors.... im constantly getting a few people per gig coming up and commenting on how amazing the sound is. the comment i always get is ( " i felt like i was at a stadium gig, it was amazing "), but for me being a musician and someone who enjoys good sound, its nowhere near where i would like it. 

i need to be able to cover up to 1,500 to 2,000 people comfortably if need be, in the smallest and lightest package as posable, having a bad back means the rest of the band has to move the rig. so i have to keep that in mind. and to be honest i can just about push the bose system enough to get away with it on as good day, ( by using the stage monitors and centre fills) , but like i said its constantly clipping. my issues are the kick drum doesn't have nowhere near enough punch and thud, and i struggle to get the vocals loud enough at the back of the room. 

ignoring the kick drum issue for now, because i think thats pretty easy to solve with some kind of folded horn subs.. ive been looking into the original ways of doing things in the 60s and 70s, ( because in my opinion the old ways have always been better ) with the WEM PA Columns. im considering building modern day versions with high powered modern drivers.. as mid high boxes, but with enough low end to be used standalone if needed, in smaller venues for the kick drum. 

im looking at either 4x12 or 4x10 boxes with a horn HF driver on top.. im trying to workout my likely max SPL and highest and lowest Useable frequency of the box itself regardless of the drivers i put in it, because i know you can only make a enclosure go so low and so loud due to its size. ..

the original 60s enclosure sizes are ( 4x12" _ 55"H / 16"W / 10"D ) and  ( 4x10" _ 48" / 14" /10" ) can anyone give me an idea of the frequency and SPL limitations of boxes that size ? and if porting them would help as the originals were sealed.

if i had my way id go to a completely horn loaded system with separate low, mid and high boxes, but there's no way with the size and weight of something like that. and the fact that one day we might be playing in a venue that holds 1,000 people and the next day in an venue that holds 80 people. it needs to be as small as posable.

any ides or info would be greatly received

Thanks
Luke