When it comes to brass, these are the best items Soma is going to encounter in the game. They are as follows:

•Sword - Claimh Solais
•Armor - Dracula's Tunic
•Accessory - Chaos Ring
•Bullet Soul - Mega Twister (Red Minotaur)
•Guardian Soul - Depends on your build. For raw physical damage, Strength Booster (Great Armor) is the go to. For magic, Blessing (Sky Fish) is optimal. Overall for traversing and general gameplay though, Black Panther reigns supreme as the speed boost of this game.
•Enchanted Soul - Headhunter, no questions asked.

Each of the mentioned items or souls can be obtained as follows:

Claimh Solais can be found in the Forbidden area in the lower east portion of Castlevania. You'll need Undine in order to go underwater into the lower portion of the ship. When you reach the dead-end on the left, hit the wall a few times and this greatsword is yours! The reason this weapon is so good is because it
a) has the holy attribute
b) can be attack-cancelled, making it the highest DPS weapon in the game.
c) The attack arc is enormous

Dracula's Tunic is located on the Top Floor, after the boss fight with Graham and alongside the Black Panther soul. Dracula's Tunic is the best overall armor in the game, but Death's Robe gives a slightly higher INT boost for the magically oriented. Black Panther just rules.

The Chaos Ring is located at the highest portion of the Chaotic realm, and can only be obtained after reaching 100% soul completion in the bestiary. Considering you can't lose MP with this ring equipped, even when cursed, provides a huge benefit over every other accessory. This especially holds true when casting MP intensive spells like Mega Twister.

Mega Twister is dropped from the Red Minotaur enemy. These guys are all over the castle, from the Arena to the Top Floor and even the Chaotic realm. However, Mega Twister does have a rarity of 80 so you may have to grind for a fair bit to get the soul. On my run on the steam port it took me over 30+ minutes with one shotting via Killer Mantle. Don't fret though, as the grind is worth it. Mega Twister does a ridiculous amount of damage and is fantastic for grinding boss rush rewards!

Headhunter is acquired early on from the Headhunter boss in the Inner Quarters.

There you have it! Hopefully with this information you too will be able to roll over everything in the castle with this equipment!

Smithygon - Sprites - https://www.spriters-resource.com/game_boy_advance/cvaos/
Castlevania wiki - other sprites/info - https://castlevania.fandom.com/wiki/Castlevania_Wiki