Your 870 is a better gun that all of those you listed.
Find a trap club and get some experience before spending money. If you buy cheap, you'll have to buy again. You're better to buy a good used gun than a cheap new one. I started with a Beretta 686, then a Browning BT-100 and now I shoot a Perazzi TM1 and a Perazzi MT6. I bought all of them second hand except the Beretta and I would have saved a lot of money if I had just bought used in the first place. Probably, the best you can do to start on trap is a Browning BT-99, or a Beretta 682 for trap and skeet.
Keep in mind, I'm not criticizing the guns you listed, but they are not designed for trap. They are good for what they are intended for, which is hunting.
Find a trap club and get some experience before spending money. If you buy cheap, you'll have to buy again. You're better to buy a good used gun than a cheap new one. I started with a Beretta 686, then a Browning BT-100 and now I shoot a Perazzi TM1 and a Perazzi MT6. I bought all of them second hand except the Beretta and I would have saved a lot of money if I had just bought used in the first place. Probably, the best you can do to start on trap is a Browning BT-99, or a Beretta 682 for trap and skeet.
Keep in mind, I'm not criticizing the guns you listed, but they are not designed for trap. They are good for what they are intended for, which is hunting.